My car won't start. Car was working fine till about a week ago code P0123

I turned the car off and wouldn't start back up the next morning. I just got this car in feb. I got everything fixed when I bought it. If I would leave the car on for a while like 1 hour like not shutting it off letting it idal the servise light would come on and every time it shifted It would give me a kick. I had that looked at and no one can figer out whats wrong.

So resently I Check the oil about 6 weeks ago it was reading no oil so I put some in ( there was somthing wrong It wasnt picking up like it was( when I laid on the gas wouldn't go as fast)) and the next day the car was blowing white smoke out the exsost had it looked at and told me there was too much oil in it. Ok so they said I didn't cause any damage to the engine. So was working fine till it started to stall ( I parked on an incline and tryed to start it.

It didn't want to it took me a good 5 of turning over the engine till it fired up) the it was working fine untill a cupple days later I tried starting and nothing the engine turns over but wont start. I ran the battery dead had someone jump me we waited like an hour and finally started but the car was running tarible ( when changing gears it would like drop kick then pick up it was strange then after it worked up it was fine started right up) took it home and now won't start at all. I put heat in it no changed sparks Checked the fuel injectors cleaned everything I took out, put it all back and nothing.

We check all the fuse checked the fuel filter. I took it to the shop got the dionostic and the code it gave me was p0123 and throttle posiotion senser and I can't find where that is I took the trotted body off. And that's where I am