Good pronunciation should be one of the first things that you learn. You can live without advanced vocabulary, because you can use simple words to say what you want to say. You can live without advanced grammar, because you can use simple grammar structures instead. But there is no such thing as “simple pronunciation”. If you don’t have good pronunciation, you have bad pronunciation.
And the consequences of bad pronunciation are tragic. Even if you use correct grammar, people may simply not understand what you want to say- even if your choice of words and grammar are perfect.
If you speak German with a strong foreign accent, you are making it difficult for people to listen to you. If native speakers struggle to understand your German, they will want to avoid talking to you, if they have the choice. On the other hand, if you have a clear, pleasant accent, people will simply enjoy talking to you. They will want to spend time with you- and that’s a fabulous feeling!