What happens to transactions included in extinct or invalid blocks?
what happens if my transaction is in the fake block?


It is also in the memory pool (mempool) of pending transactions at other nodes run by more honest people and will be included in a new and valid block in the normal way.


  Let’s suppose I am buying a Tesla car. Should I wait 6 blocks to be generated to be sure? But I have to wait 1 hour!


Yes.

There are faster payment methods for Bitcoin - e.g. Lightning Network (LN) and arguably perhaps escrow services. But they have their own trust model and characteristics you need to understand when using them.