How to repair holes in the crotch of my Tenpenny Pants

I saw those,but I wasn't sure if they would work on a non-flat bit of the clothing (the crotch is a kind of saddle shop on most clothes)

I've done it on elbows. I put a patch on both sides and sometimes hand stitch the corners down so they don't curl up. eBay has patches but most come in from China (I've had a set of denim patches ordered now for a couple of weeks but the shipping now says VOID). You can probably find them in the states just at a higher price.

Clothing starts out as a flat piece of fabric and has curved seams to fit your shape. You can smooth down the area to where it’s flat and add a patch. You’ll follow the curved seam to keep the shape. If you are hand sewing use a back stitch which is strong and won’t loosen. For a source of patches try your local fabric stores. You don’t have to use a precut patch, you can cut your own from new fabric or my favorite, old pants ( which are already softened from wear). Denim will fray on a cut edge so just put the patch on the inside if that’s not what you like. or enjoy an edgy look.

I love that ifixit supports repair solutions!

I’d like to know how to make the crotch longer as it is short counting from the waist and feels uncomfortable to wear

Sorry, I believe the correct word is hanger not crotch. The pieces that goes from the waist to the crotch.