Car start issues and codes P1260, P0212, P2122, U1900, P0231and P0571

Hi

I am an owner of the car listed above Flexifuel and have lately been experiencing issues with the car. It started 2 months ago when I couldn’t get the trunk to open. Then a few weeks later I couldn't get the car start at a car park. I had to get another car owner to charge the battery using jump cables after which I got the car going with no warning lights and drove home. I initially thought that the battery needed changing but then I remembered that the battery is only two years old, so maybe the issue is not with the battery. I could drive the car for a couple days with no issues. Then the issue started again. I had parked the car and an hour later I couldn’t get it to start. After trying for about half an hour I eventually got the car to start and drove home. This time I got a yellow engine check warning light on the dashboard. The next day I turned on the car and the engine check warning light was gone but I took the car to mechanic anyway who conducted a troubleshoot that displayed the codes below. He erased these codes and told me to come back in a week. He claimed that there isn’t anything seriously wrong with the car but I have continued to have issues with starting the car after parking for less a a couple hours. The issue with the trunk has remained but at times (very few times) I can get the trunk to open. Can you please tell me what the issue could be? I want to take to another mechanic but I am scared that I will get ripped off as I have had bad experiences with mechanics.

Here are the codes the mechanic found in the troubleshoot:

P1260
P2121
P2122
U1900
P0231
P0571

Thank you in advance for your help.

Robin