1998 bmw overheating at times has had the waterpump

This is typical of BMW 318 and others I suppose.
If after changing the radiator, the hoses, the water pump then the other cause is leakage of coolant at the back of the engine block.

This is hidden but there is a hard plastic outlet which gives away after 5 or more years. If the leakage is serious you can notice the coolant disappearing very fast.

Worse it could be the gasket leaking.

when you removed the radiator hose was there orange sut in side it if there was then you need to change the thermostat remove the on eit already has dip it in boiling water to see if it opens if it dosent then that is what is causing the overheating problem