1993 BMW 318 battery problem

Electrical problem
1993 BMW 318 4 cyl Two Wheel Drive Manual a lot miles

Hello,
I just get old BMW 318i from my friend, told it needs just some little repairs. I already spent 1700$ for change the tires, alternator, new battery, track and fix the wires (it was burning fuses sometimes), exhaust pipe and something what keeps the wheeles fixed by the car (i dont know what was it, but it costs me 950$). I have had problems with the battery, but thought it will be fine after fix the electrical problem and change battery, but it is not. The battery is 2 weeks old, and after leave my car for 3 days outside I could not start. I jumped the car and drove home about 10miles. I was fine in the morning driving to work-7miles, fine to drive to lunch 0, 5miles, but at the evening I had to jump the car again. I really do not know, where the problem could be now. Is there something else needs to be replaced? Or is the problem that I drive only 14 miles a day, 5 days a week? I was checking internet and found some advices like put the "trickle charger" going to cigarette lighter or fix the"final stage unit" or "dome lights sensor". I have no idea about cars, I need to know if there is a way how to fix it, and what needs to fixed.
Thank you very much answer

young blond girl with old black car