Need Advice Setting Up Wifi Network for 40 Active Users

Hi guys, I've been having hard time getting 40 active users on a WiFi Network to work well. So the goal is to get all of these users to connect to a single local server and run a web-based e-learning application smoothly.

My current setup is like this:https://photos.app.goo.gl/THWYKV3PjtFiSWrq5

All of the wifi routers is a consumer-grade Wifi router, the ones typically used at home or small office. (Like one of those 20-30$ routers). ROUTER 1 is connected to the server through LAN cable. ROUTER 2&3 are connected to ROUTER 1 through LAN cable as well. Users are split evenly amongst routers via WiFi which are password-protected and each has different SSIDs

Current problem is that once I hit > 30 users, the whole thing often hangs or the connections to the server timeouts/delayed. The server doesn't seem to be the problem because CPU usage is still low when it happens (<10%) and network-wise I think the server is also fine because each of the client is just using something like 100 KBps and they're not even active all the time, because they're just accessing a web application.

I found out that when a hang happened, restarting WIFI ROUTER 1 recovered the hang. After that, the connections seemed to be pretty good for a while before another hang that requires a restart happened again. This got me thinking that maybe the bottleneck is that WIFI ROUTER 1 couldn't handle all the packets from 30+ users? I'm thinking of buying a gigabit switch and have all of the routers and the server connected into it, to replace the role of ROUTER 1 as the switch as in the setup above.

Do you guys have thoughts or advice?

Thanks in advance!