Need help with logarithmic function

[Margooox]

Hello everyone!

I have a database in Google Sheets of materials (leather, steel, etc..) that have different modifiers (100%, 70%, etc...). This creates a curve that interpolates between the points.

My issue is that in Master!D:D I wrote the following formula:

=IF(E3<0, INDEX(MaterialData!$A$1:$F$13, MATCH(C3, MaterialData!$A$1:$A$13, 0), MATCH("Damage Modifier 1", MaterialData!$A$1:$F$1, 0)),
 IF(E3<=-20, INDEX(MaterialData!$A$1:$F$13, MATCH(C3, MaterialData!$A$1:$A$13, 0), MATCH("Damage Modifier 2", MaterialData!$A$1:$F$1, 0)),
 IF(E3<=-40, INDEX(MaterialData!$A$1:$F$13, MATCH(C3, MaterialData!$A$1:$A$13, 0), MATCH("Damage Modifier 3", MaterialData!$A$1:$F$1, 0)),
 IF(E3<=60, INDEX(MaterialData!$A$1:$F$13, MATCH(C3, MaterialData!$A$1:$A$13, 0), MATCH("Damage Modifier 4", MaterialData!$A$1:$F$1, 0)),
IF(E3<=-80, INDEX(MaterialData!$A$1:$F$13, MATCH(C3, MaterialData!$A$1:$A$13, 0), MATCH("Damage Modifier 5", MaterialData!$A$1:$F$1, 0)),

While this "works" it lacks granularity which makes it inexact. I would need a system that can take -73.5 and find the exact value from the curve, not just a broad bracket from -60 to -80.

I'm not great at math and am not trained in Excel/Google Sheets so I feel unsure as to wether I have the right idea with needing a logarithmic formula or if maybe it needed an array?
I tried making my own logarithmic curves but I need to make a curve with several bases (for my modifiers).

Any help or advice would be highly appreciated!

Feel free to add your own tab to the sheet here.

Thanks in advance!