Google play store!

I have a problem with my android phone - the google play store stopped working. Until then, I did not know the importance of this application. And wow, it has been difficult without it!

Perfect! There were no problems with grammar or vocabulary and nothing needs to be changed. My first suggestion to make it sound a tiny bit more natural is to say "didn't" instead of did not - we always use the contraction unless it is in an essay or something like that. Also, for your last sentence, you could say "And wow, it has really been difficult without it!" The word really is not necessary here, but we often add it in this kind of sentence to emphasize the feeling.

Really good job!