Reading Japanese

Japanese words are stuck together so are there any tip on how to know when a word ends and were another begins when reading words that you don´t know?

Separating everything out just comes naturally as you learn, but verbs are pretty distinctive on their own since they always usually end with う/る/ます if that helps.

Is the text you're reading all in hiragana, or is it written kanji as well?

If you're just starting out in Japanese it's something that you'll just end up getting used to eventually. There is no real rule or step to follow in learning how to distinguish what is one word and what's the other (especially when you are using all hiragana and no kanji). It's just the more vocab and grammar rules you learn, the easier you'll be able to read everything.

As yllwsmrf implied, even for native readers, it is indeed difficult to know where a word ends if it's all written in one type of kana.

For this reason, reading material for young children such as manga are very often written with spaces in between words.

But adults can tell where words part by kanji, katakana and punctuation. In other words, when adults write Japanese, it's important to insert kanji, katakana and punctuation every now and then so that the reader can read properly.

Example:

difficult to read
ははははがないははははは

easy to read
母は歯がない。ハハハハハ！