Schachfreizeit
So would you recommend buying additional practice test? I would assume that those practice tests have questions from different question banks.
I've also read a post where someone said you reinstall a practice test, but I don't really understand the point behind this.
Yes, it's probably a good idea to buy additional practice tests, but don't just burn through the official tests because retaking tests 3 - 6 isn't great since their question banks are not large. Thus, if you retake them, you'll see many repeated questions. So, if you just run through the tests, you'll end up with none later on.
Instead, wait until later in your prep to take more official practice tests. If you want to practice handling the test experience, you can use third-party tests for now.
I'm not sure about reinstalling the tests. In the past, the tests were downloadable, but they no longer are. So, I don't think the idea of reinstalling them is relevant at this point.
For more on how to use practice tests, see this post.
Taking GMAT Practice Tests