Why is my transmission not shifting properly?

Question

Sometimes my truck shifts fine. Then out of nowhere it seems I lose drive and 1st gears. I only have 2nd and 3rd gears. Transmission does not want to shift on its own all the time. It does not feel like it's slipping it's more like it doesn't or can't shift properly. Also the engine light came on the very first time it happened. All fluids have been checked and are clean and at proper levels. The codes that I have are as follows:
P0740
P0753A
P0758D
P0785
P2761
Any help is greatly appreciated. I am attending welding school and my truck is all I've got to get there with. Should have taken automotive school first. Lol thanks for your time.