If your fuel pump is leaking does it mean you have to change your torque converter

No, the two are unrelated. 5k just for a torque converter is very high, Take it to an independent shop for another estimate.

You are at a Mercedes dealer? They are the experts- you have not explained this problem clearly enough here- have the service adviser explain it to you- It is impossible to give you advice specifically without more info- but in general I can tell you, that you are driving a very expensive, high performance (AMG) car- these things don't come cheap- to go 150 MPH that machine must be perfectly maintained- and preferably at the dealer- you have already hit on your solution- sell the thing- we live in an age where a new bumper for a KIA costs $1500- 5 grand is nothing for your car- it should cost 10s of thousands each year to keep that car in perfect shape-

Thank you so much for your advice. My sister gave me the car and offered to pay half for repairs. However I did not know it would be so expensive to maintain it. If I will make a good profit I will get it running and sell it if not I will sell it as is and get whatever I can thank you