What should i expect

Im going to Japan in about a year and ill be 17 at the time. I have red hair and im about 5 9" I speak some japanese to get by. Will there be any social problems or any problems getting a Girlfriend... Just basic stuff like that.

I guess you will not have problem's but be ready to live a majeur change i dont know were you live but im shure that its not the same lol You will be fine Japan is one of the beast country in the world Just learn the most Japanese you can thats my advise and dont worry the first days you will maybe feel really really all alone but it will be better after the first days
have a lot of fun on you trip

You will stand out as a foreigner (your height or hair colour don't really matter) but how the people react to you or whether you can get a girlfriend here depends entirely on your personality and attitude. Also the more Japanese you speak the easier you will find it to meet people.

If you are comfortable making new friends/ talking to girls in your home country, you will most likely be okay here after you adjust. Beyond that it's up to you- everyone has their own expereince in Japan, we can't tell you what will happen.