Recommend a protein supplement?

Cycling does not give you strong legs. It prevents them from wasting away but doesnt really add any considerable strength over someone with similar genetics who doesnt exercise their legs that often. I know that from comparing myself to my two brother both of whom are total couch potatoes. And also when I started weightlifting at the beginning of this year I could only squat 40kg and at a piss poor depth too.

Cycling (especially a well fitted road bike) uses legs over a very small plane of motion and only on one axis. There is no heavy loading or stability challenge. Someone who rides mtb would have a lot stronger legs from intense stand up pedalling up bumpy hills.

I am now upto 77.5kg deep squat 5x5 (BW at 68kg) shooting for 105kg by end of year.

Can also climb a rope but not with arms only like mr chug it.

On your squat or for your bodyweight?

I take it by that rep range you are doing a 5 x 5 regime, or westside barbell, something along the lines of that?

You maybe want to look at a higher rep range before you start moving up in weight, those regimes are designed to help seasoned lifters break through plateaus not people just starting out, they won't work the muscle enough, at least not on their own anyway.