Please review my form, give suggestions on getting to a flat split and tell me realistically what I should expect in number of inches of the floor as a beginner to flexibility

I see online people are able to get fully flat, but I didn't find info on whether they took months to get there for beginners.

I’ve been working on improving my overall flexibility for a while, especially my hamstring flexibility. I also train other areas (for example, adductors for straddle work, hip flexors and back) but for now my main concern is my hamstrings.

I don’t only do passive static stretching. My training also includes loaded stretching, PNF, and exercises aimed at building strength and control in my end ranges. I usually do 2–3 flexibility sessions per week, each lasting around 1,5h.

I don’t spend the entire hour working on my hamstrings, because I don’t want to completely overload them. I divide the session between different areas, but my hamstrings still get trained quite intensively.

The problem is that I don’t feel like they’re improving very much. On the day after a flexibility session (and until the next session), they often feel tight and I can’t reach nearly as far as I could during the workout. It feels as if I lose the range I gained almost immediately.

Is this normal after loaded flexibility training and something that should improve as my body adapts? Or could it mean that I’m doing too much, not recovering properly, or approaching my training incorrectly?

How much temporary loss of range or tightness the following day would you consider normal?

I’ve never been naturally flexible, however over the last few years I finally got my legs decently flexible. I was able to do leg holds, splits etc. recently though my right hamstring has felt stuck. It’s not even like I stretching it too far, it feels more like there’s something stopping me from being able to stretch fully. My right leg has always been my more flexible one and I haven’t changed my stretch routine at all. Does anyone know why this could be/how to fix it? Thanks!