Can I use diferent criteria in an IF statement such OR

My formulas work great as written but I have 1 condition that causes the
formula to return the wrong result.
the solution for an earlier problem was to refference the formlas by
putting them in separate cells and simlifying my result to conply with true
or false and this solved the major issue =IF(C11<100,P2,Q2)
however another problem has arisen since the calculations are dependant on
other factors
once C11 reaches 100 if L5 is not = or 500 the result is in error but the
formula in P2 still meets the criteria
I need to n=know how to make the following work
IF C11<100 & L5<500 then P2 because otherwise everything works as it should
the problem only persist when C11 is - 100 and L5 is < 500