2006 check engine lights including red triangle

So I have a 2006 I’ve been having a few problems for several weeks now after replacing the camshaft, I have to get a new diagnosed due to all the lights coming on Estates that I have poor engine power, throttlebody, Cadillac converter needs work on and also I have the big triangle that came on the mechanic told me the big triangle deals with the main computer of the car. The check engine, light and triangle would come on then all of a sudden the other lights would appear for a short period of time. Then the red triangle would go away, only leaving the check engine light on. Now, as I was driving, all the lights came on, including the brake, etc. and there was a loud beeping noise Has anybody experience this or can help.