sometimes for fun I make sv_maxspeed and cl_forwarspeed 9999. I forget to fix it sometimes. in userconfig.cfg

sv_maxspeed 320

cl_forwarspeed 400

Is there a problem if I write these codes or are these values correct?

sv_accelerate 10
sv_friction 4
cl_backspeed 400
cl_sidespeed 400
I thought of adding them like this, are these the default values?

Runs must follow the command whitelist that can be found HERE.

If you have any doubts about default values, you should visit Valve Developer Community website that contains a list of all hl (and other games') cvars with their default values.