what happenes to the speed

Good morning,

I'm confused so when I'm using my internet, (also keep in mind i am hard wared to the router) my mps is all the way up to like upload 200-300mps and download 700mps but as soon as anyone uses it, it drops dramatically goes to 30mps upload and download 40mps and that's just one other person using it. I use this for my work and can't be dropping calls. Do I need to get an upgrade and if yes how. Because I have 3 tvs, 7 systems, and 3 phones that will be connected to it.