Bus, I buy Gator mulcher blades on line.
I do not sharpen them before installing
A bent blade should not be straightened; replace it.

The edge of a lawn blade should NOT be like a razor or even a knife. The reason it should NOT be knife-like is because that type of profile only lasts a mowing or two and it becomes ROUNDED off.
A knife edge is too weak to withstand the thrashing it receives from grass, twigs, and fine grit present in the average yard and will therefore lose material and reshape into a rounded profile. A rounded profile does not lend anything to severing the grass stems (further described below).
The best and longest lasting edge is one that has been sharpened to a reasonably "knife-like" profile first, and then the knife edge is "squared" by using a shop mill file until there is a 1/32" to 1/16" flat edge that is going to hit the grass stems.
The squared off edge is better able to withstand normal impacts because it presents a larger "face" at the point of impact.
The edge profile of a properly dressed mower blade presents a 90 degree (approx.) angle on the bottom of the blade.
It is this 90 degree edge that takes care of "severing" the blades of grass when the mower blade strikes them at high speed.
Think of cutting a blade of grass as if you were trying to tear a sheet of typing paper in half. First thing you need to do is to fold and crease the paper along a straight line. Then you carefully tear the sheet in half by pulling in opposite directions along that creased line.
The squared bottom edge of the mower blade provides the straight surface that is going to "fold" the grass when it hits, and the high velocity of the mower blade provides the "pull apart" action that severs the grass stems along that sharp "fold line".
The higher the blade velocity, the better will be the severing effect.
Most of the cutting is done by the mower blade tips within 1" of the end of the blade. The rest of the blade edge just thrashes at any "stragglers" of grass that got knocked out of the way when the tip passed by on a previous revolution.
For a person who is not reasonably handy and/or does not have basic shop stuff (grinder, vise, files) the best way to address blade maintenance is to have a spare set (or 2) of mower blades and get them sharpened professionally.
Sharpening blades requires checking and adjusting blade balance.