1995 BMW 525i OVRALL PERFOMANCE

Please help me, I had a good running automatic BMW that I bought because I had a serious op on my left ankle and were left with 5 screws in it, and this is where all my problems started.
I purchase a 1995 BMW 325i from BMW: kl- 110,000. Five hundred kilometer’s LATER I had some work done to the car, meaning BMW changed the water pump and thermostat and all water pipes connected from the radiator, the radiator was redone and as good as new because the car suddenly overheated. I was told the electric part next to the automatic shift is worn out and needs to be replaced, it’s the reason the car was so slow in changing. The engine ran poorly. It struggled to start and smoked when it started; it also idles uneven and struggled to move until it stops smoking. I have lost all respect for BMW her in Brasilia and are at end with patience. Every time it goes in it comes back with another problem, it feels like the mechanics are causing more work to be done, and I still sit with the same problems and more, unfortunately there are only one BMW agent in Brasilia leaving me with no alternative to make use of any other workshops. All I want is for the car to start first time and idle properly, cane u please advise me on what the problems may be, so these mechanics can stop lying to me, it will definitely help me in all these problems, I thank u kindly from Brasilia
Bennie Carstens