I am not sure what you mean.

You wrote:
I thought, when AND is used all conditions should be met, not partially like OR.
But in your solution, if E5 and N5 are >=50 it would give TRUE.

Yes, all conditions must be met for AND to return TRUE
If E5 and N5 are >=50 but any of H5, K5 or Q5 is < 50 my formula returns a blank.

AND returns TRUE if all conditions are met, otherwise it returns FALSE.
OR returns TRUE if at least one condition is met. Only if none of the conditions are met it returns FALSE.

As to your last clause - can't you upload a file showing the problem? Please include so much data that it is possible to test and state manually examples of expected results.