@upaxgunxgrave Volume training. Higher rep, many sets (5 X 15 then 5 X 20 then 5 X 25 etc)
Don't go to failure. Make up for it by training push ups 4 times a week.
And a 3-5 min L sit will take a few years I reckon, where as 100 push ups could be achieved in 6 months or less for an average...