The claim I’ve heard most is that Kalashnikov based the design of the AK-47 on the STG 44, but I’ve read a comment on this site (as far as I can remember) from a user whose username I can’t remember who said the opposite: That Kalashnikov did not base the design of the AK-47 on the STG 44
They have some cosmetic similarities and share some congepts but there are even more differences, especially in regards to how they operate and are engineered. So the ak 47 isn’t really based on the stg 44 so much as they resemble each other a bit and are from the same time period