Komatsu PC220-6 Hydraulic Problems

Hello everyone new to the thread, just want help and experts advice on isolating the problem. When i turn on the excavator and move the the machine or dig something it works fine but after working for a few minutes i noticed that digging and moving starts to slow down and finally its cant move. i've already replaced almost all of the internals on the main pump and tried cleaning the strainers and oil filters. any help or suggestions would be appreciated. thank you

Komatsu PC220-6 Hydraulic Problems