Wheel mouse not working properly and not being able to use Fn key as sprint

I'm having problems I use not to have. When I recently updated to Minecraft 1.13 my mouse wheel started acting weird, when I try to switch items in my hotbar it will take some time for me to get it to work. I thought it was my mouse but when I got to a latest version it worked correctly.

 

The second issue I have is that I used to sprint with the (Fn) key and I no longer have the ability to use it. I really don't understand if it was intentional but it's really uncomfortable to play like that. 

 

I hope you can give me an answer to this problems me and some of my friends are having.

Thanks.