Signal issues

I am a bit overwhelmed with all the posts and just don't know where to begin looking for my issue, mainly because I'm not really certain what my issue is.

I live in a large ranch style home and my router/modem is in the back bedroom of the house on the desktop. We have 3 laptops and smartphones used throughout the house. We also have another desktop at the other end of the house. The cable company has been out numerous times to try and fix the issue of poor signal strength. We have their "best" router/modem. Their only suggestion is to run another ethernet cable under the house to connect the two desktops. That solves the issue for the desktops, but not the wireless ones.

I simply want to be able to move freely around my house and have good signal strength wherever I go. I can't seem to get a clear answer to resolve my situation. Is there a stronger router/modem I could purchase, could I run the ethernet cable to the other desktop and have another router/modem that broadcasts a signal along with the one in the back?

I am just frustrated and don't know where to start to solve this issue. Thanks for reading

Use multiple wireless routers.

That is what I wanted to know, I will try it out, thank you so much!