Is there an expression or something which directly checks what the player types in, instead of running the GetInput script every time? Because there are some downsides to it.

I only know of 'get input' and the use of Commands, for getting direct input. Maybe there's more ways, but these are the only 2 that I know of.

What are the downsides that you don't like, as maybe there's ways to deal with them.

well, one downside that I noticed is, that the script consumes a turn. or that it takes a turn to react to what the player types in. cause it first checks the input and then does something according to it. maybe I do it wrong because I use it in this way:
I use it to check what command the player is using because I just want a reaction to the commands that work and make sense to the game (I would clearly state those in an instruction).
so i check like this:

get input
then
if result = "look around" or whatever
then etc.

is there a better way to do that?

If you want to do all the input processing yourself and not have any of Quest's normal handing kick in, then take that HandleCommand function I gave you before and gut it. Then put your own command handling logic inside. It will go through the standard Quest input mechanism, but you'll be able to do whatever you want with the input once it's entered. That would be simpler than using get input everywhere (in my opinion).