Too many questions that can be answered by some research here. But, I'll bite.
I was wondering if I can really put it in the water because the technical sheet savs up to 50 meters of water. depth and I don't know if I should trust it
You should not. You need to take the watch to get professionally water tested for leaks. Normally an easy test and cheap to do. I had a ZF GMT Tudor that I pressure tested and thank God I did, the crystal was not seated correctly so it popped off during the test.
What do you think about the watch? Have I made a good purchase?
ZF is known for being the best Tudor maker. You are the judge when it comes if you made a good purchase or it is a good watch.
And what do you think about the Movement Asian 2836 automatic movement 28,800 VPH?
The Asian 2836 movement is a workhorse movement in the rep and gen industry, preffered for its ease to service and replace it things go wrong. I prefer them personally as they have become so affordable to get brand new that I just swap them instead of getting them serviced. A new movement is $90 while a service can get to the high $200's.
Just so you are aware, Geektime is not a Trusted Dealer here so anything regarding your transaction is on your own.