pump won't cut off(new hardware)

pump would'nt cut off.replaced water tank,pressure switch,and gauge.pressure holds at 35psi and won't reach the cut off.can adjust pressure switch,but pressure still won't rise above 35psi and pressure is weak like that.water almost stops running before pump turns on.it is a submersible pump.how do i get pressure to go back up to 50psi like it should?

You have a leak underground or in the well. Is your water dirtier than normal? You can pressure check the water line coming through the foundation. If it builds pressure or little to no pressure and drops to 0 on shutoff you definitely have a leak. Repeat test at wellhead and if results are the same then leak is in the well. After you do repair it helps to repeat the tests just to confirm that you have no additional leaks in rest of well system.

What are the on / off settings of the switch?

What is the air pressure set at in your tank?

Did you check the 1/4" tube going to the switch when you replaced it to be sure it was clear?