You need to spend time creating a system that allows you to add to the code without it becoming messy.
Maybe make a list of effects all set to true. This is what your character can do in a normal status.
If you go to jump it first runs a function check - can you jump? - jump came back true so jump else ignore command
While crouch = true set jump false and MS 0.5
Now if you jump the function will ignore cause it will fail the check.
I’m the end it should just be -
Player is crouching
Player is sick
Player is slowed
Function
Player can’t jump
Player can’t run
MS 25%
Player can’t stand
<everything else still true>