Vitz 2003 Automatic Gear problem

Salam

Friends im facing a big big problem now a days, idk how to explain, but let me try;
MashALLAH sai I bought a silver sleek shined vitz, totally remarkable, and hot running car,3 weeks ago, it had some scratches and some front bumper work has to be done, i did all of that work after buying from him and plus i modified it a bit. Now the car is in a shape. After completing all the work i again visited him to show him his car after it got modified, and then jab usnai garhi dekhi to he kept saying k sell me the car, i want it back, it was really awkward but phr bhi i said i cant, im loving it. Then after 2 days, he said k bhai menai tumhe bataya nahin tha per is garhi mein gear ka masla hai, i was like !! hain ! he said is ka gear box khul chuka hai aur falah falah, now i really dont know what to do, i thought to sell the car but im in love with this car, im really puzzled. ONE thing also, he's still saying k mujhai bech do main is garhi ko bikwadunga phr, mujhai samajh nahin araha hai k agar gear mein masla hi hai to phr woh wapis Q le raha hai woh bhi zyaada paison mein. He said he knew one of his mechanic, and i visited him as well but i think usnai us mechanic sai pehlai hi baat kar rakhu hui wi thi, he did nothing just drove the car and said k is k gear jaley hue hain bas! WTH !!! thats not called checking, btw PLZ PLZ PLZZZZZ

u Ppl can really help me out in this matter, just suggest me a good mechanic who knows the gear thingy of vitz or who really has his own mechanic and can take me to him or can give me his no. I really wanna keep this car and dont wanna do stupid things aur main bewaquf nahin banna chah raha. PLz help me out, mujhai is k gear box check karana hai.

I live in karachi. Suggest me a good mechanic over thr. THanx alot
I hope u guyz will help me out !

tc Allah hafiz! Do reply!