Just install SSD now Mac not perfoming

[thewall]

After having the flashing ? on a 2015 27” with Fusion Drive I managed to get the old HD running ok on Mojave,so as I had the kit to put a SSD with Big Sur installed when I had the SSD as an external drive, everything went ok until I switched it on, it takes an age to load from start up or restart, and when I put it to sleep it won’t wake, also once passed the login screen the letters lopikjhm don’t work on the keyboard but they do on the login screen.