Nesting Formulas

Hello Smartsheet Community,

I have a formula in Smartsheet that works:

=IF(ISERROR(MATCH(5, [Risk Rating]3:[Risk Rating]19, 0)),IF(ISERROR(MATCH("HIGH RISK", HIGH23:HIGH25, 0)), IF(MEDIUM26 > 935, IF(ISERROR(MATCH(5, [Risk Rating]17, 0)), "HIGH RISK", "VERY HIGH RISK"), IF(MEDIUM26 > 310, "MEDIUM RISK", "LOW RISK")),IF(ISERROR(MATCH(5, [Risk Rating]17, 0)), "HIGH RISK", "VERY HIGH RISK")), IF(ISERROR(MATCH(5, [Risk Rating]17, 0)), "HIGH RISK", "VERY HIGH RISK"))

And I want to add an IF statement  that IF MEDIUM26 is 0 result is NOT DONE.

 I thought removing "LOW RISK" from IF(MEDIUM26 > 310, "MEDIUM RISK", "LOW RISK")),  making it  IF(MEDIUM26 > 310, "MEDIUM RISK"), and then adding  IF(MEDIUM26 > 1,"LOW RISK", "NOT DONE") would do it, but new to this and have been struggling with getting it to work.

All I want to do is report "NOT DONE" if cell MEDIUM26 is 0.

Then my result would be either VERY HIGH RISK, HIGH RISK, MEDIUM RISK, LOW RISK or NOT DONE.

Any assistance would be appreciated.