help with japanese grammar

hi!i am a student of japanese and,while i am studiyng i found some problems with grammar!
may someone help me please?

1)i haven't understand well the meaning of the particle ''ka''.i mean,in this phrase,what does it mean?
-jibun ga dono gurai jyouzu ni natta KA wo itsumo kangaeru youni shiteiru.

what is the right translation for this sentence?

2)what does this mean?
-A dakede(ha)naku, B.
it is something like: not only A but also B ?

3)i really cant catch the meaning of the expression ''wake ga nai''.
for example,how would you translate this sentence:
-mochiron eigo de tegami nado kakeru wake ga nai.

and finally ''hottoshite itara 'anata no eigo ha kanpeki da' to iu ....''
what does this -tara mean?how do yuo translate it?

i hope someone can help me!
onegai itashimasu!
and sorry for my terrible english,it is not my language:(!

1)i haven't understand well the meaning of the particle ''ka''. i mean, in this phrase, what does it mean?
-jibun ga dono gurai jyouzu ni natta KA wo itsumo kangaeru youni shiteiru.

This "ka" is used at the end of a question clause embedded into the sentence.
So in the above sentence: "jibun ga dono gurai jyouzu ni natta ka" = "how much better I've gotten." So the whole sentence says:
"I make it a habit to always keep in mind how much better I've gotten."

Another example would be:
- Ashita ikeru ka dou ka wakaranai. (I do not know WHETHER I can go tomorrow.)

2)what does this mean?
-A dake de(ha) naku, B.
it is something like: not only A but also B ?

Yes :) But it is likely to come with a "mo" after B.

3)i really cant catch the meaning of the expression ''wake ga nai''.
for example,how would you translate this sentence:
-mochiron eigo de tegami nado kakeru wake ga nai.

"There is of course no way that I can do something like writing letters in English."

and finally ''hottoshite itara 'anata no eigo ha kanpeki da' to iu ....''
what does this -tara mean?how do yuo translate it?

"...tara" is like "while/when I was (doing something)."

Hi, Risa san.
1) KA can be translated as how or what. E.G. Nedan ga dore kurai KA o shiritai. I would like to know what is the price.
Yours can be translated as I am accustomed to think how well I have recovered.
2) You should add MO.
So, A dake de naku B mo is, not only A, but B too.
3) Wake ga nai is, not possible . Yours can be translated as, Surely I(or You or He or She) can not write a letter in English.
4) Itara is being. Yours is, When I was taking a rest, they told me my English was perfect.

TOSHI,

For 1), since the word "jyouzu" is used, I think the sentence is talking about how much better someone became in terms of *skills* at doing something, not in terms of *recovering* from a medical condition. If it was "recovered," then it should be "dono kurai yoku natta ka"

Also "itsumo kangaeru youni shite iru" is "I make it a habit to always think about...," not "accustomed to..." desho??

I agree with AK about the translations. じょうず is used for skills,so it's unlikely for it to refer to a recovery. Also,ように,when used like that roughly translates as "to do towards" so yes,it would be referring to a conscious decision,a habit:)

arigatou gozaimasu!
thank you so much for you clear explanations!!you are really so kind^^
well,actually.i have found other things i can't clearly understand...may you help me also this time?

-what is the difference between "dekireba" and "dekitara"?
i mean,do they have the same meaning or is there a different nuance?

-the difference between -(no)you na and -mitaina?
can i use a verb before mitai?

-how would you transslate this:"tomodachi ni ha teinei ni hanashisugiru to kaette taningyougi desuyo."
in this case "to" what does it mean?

-"sono tame,keigo wo tsukawanakuteikenai youna bamen,tsumari meue no hito ya yoku shiranai hito to hanasu kikai wo sakeru wakamono mo ooi."
how would you translate this?

i hope someone would help me again!
thank you sooooo much!!
have a nice day^^

I'll come back with the others later...

-how would you transslate this:
"tomodachi ni ha teinei ni hanashisugiru to, kaette taningyougi desuyo."
in this case "to" what does it mean?

= If you speak too politely to friends, that would be distant.

- "...to" is another "if...." expression, alongside "...reba" or "...tara."
- "taningyougi" = distant, too polite and stiff
- "kaette" = (in this case) on the contrary, against your intentions

-what is the difference between "dekireba" and "dekitara"?
i mean,do they have the same meaning or is there a different nuance?

"dekitara" and "dekireba," when used on its on, meaning "if possible," or "if you can," mean the same.

When you use different verbs "...reba" and "...tara" have _almost_ the same meaning, "if/when (you do this)...." The nuances between those, and also the difference with "...to," are quite difficult to explain actually :( I'll come up with example sentences if I can, and I would want to hear from others as well :)

-the difference between -(no)you na and -mitaina?
can i use a verb before mitai?

Almost the same, describing something "like (something)," being similar to something else.

- Kono sake wa, wain no you na aji ga suru. (This sake has flavor like wine.)

- Kono sake wa, wain mitai na aji ga suru. (The same.)

When you use a verb + mitai, this means something different. Example: suppose you are trying to meet with friends, and "Bob" does not show up. You call his mobile, and he tells you he is in a strange location and cannot fine you.

- Bobu wa michi ni mayotta mitai desu. (Bob seems to have gotten lost. "michi ni mayou" = to lose one's way, to get lost)

-"sono tame, [keigo wo tsukawanakute wa ikenai youna bamen, tsumari meue no hito ya yoku shiranai hito to hanasu kikai] wo sakeru wakamono mo ooi."
how would you translate this?

Because of this, there are many young people who avoid [situations where you have to use "keigo," in other words, opportunities when you talk with people senior to you or people you don't know well].

"...wo sakeru" = to avoid (something)

I put brackets around the long phrase, [the situations where young people tend to avoid] to show the structure.