Hello everyone

I got a used Fabia 1, 1.2 HTP 12V two weeks ago. Sometimes when I start it a lot of white smoke comes out of the exhaust, but just briefly and while driving it never happened. Also, when the engine is cold, it can sometimes lose the throttle when first taking off and drop the RPM to about 600, but after dipping it a bit further it catches on. It drives rather smoothly, but today I pushed it a bit harder off the green light (changed gears on 5000 RPM) and the Check engine lighted up and throttle died (didn't have any response), but the engine didn't stall, just started slowly dropping RPM. I stopped, restarted it, and everything was fine, but didn't have the guts to go into high revs again. (Also, am I allowed to dip the throttle pedal to the floor when I want some speed, since it's electrically controlled, or should I go gradually?)

Should I be worried about that white smoke and what happened with the Check engine lamp? I should note that the car had an accident with the timing belt which skipped (two valves were replaced).

Sorry for sounding like a noob, but my previous car was a 1986 one, so I'm not quite familiar with new technologies implemented in this car.

I Also Have a used Fabia 1.2 HTP , but is the 6V version, this car  has endless problem with white smoke, , it started with the Faulty Temperature Sensor which gave the car the wrong Readings,the ECU thinks the engine is still Cold, hence Putting the Engine under stress & the Fuel Consumption Increasing,the engine light came on after this happening, But i left it Too late & its Resulted in the 02 Sensor Failing. i replaced the Temp. Sensor & the O2 Sensor and the Problem had Gone, when it came to changing the Engine Oil, the garage Recommended 5 - 30w Fully Synthetic Long life Oil, that oil seemed too thin for this type of car, i checked the oil dip stick & it was Showing on the Minimum within a few months  i topped it up again & it Dropped again,  white smoke started Blowing out again but only Briefly when Cold. I had the car Checked & they Said that the one of the Cylinders Valve Seals Have a Worn out, As the Car Has 85000 Miles on the Clock the Only solution to this was Replacing the  Oil with a thicker 10 - 40w Oil, & ad some Wynns No Smoke Additive & No more Smoke, & it has Passed the MOT Emissions Test Too.