Something is wrong with IPad Performance

OK....you have enough space available.

Let's try a simple Forced Restart on your iPad, which can often fix odd little things. A Forced Restart is recommended after iOS updates anyway.

I don't know which iPad you own, so the following covers how to Force Restart iPad with Face ID or iPad with a home button:

• Pad models with Face ID: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Power button until the device restarts.
• iPad with Home button, iPhone 6s or earlier, and iPod touch (6th generation) or earlier: Press and hold both the Home and the Top (or Side) buttons until you see the Apple logo.

Since we don't know what apps or can't see your iPad, it's impossible for anyone here to tell what's wrong.

When you say you haven't used all your gigabytes, exactly how much memory is available on your iPad? Go to Settings > General > iPad Storage and report back how much free space you really have. We can go from there once you report back.

Yes you can disconnect and reconnect, but if the router is not broadcasting a signal clearly, that won't solve anything for you. Did you unplug the router and try that suggestion?

If you did and it's still not working, make sure you know your Internet Password before you do this, but you can go to Settings > General > Reset > Reset Network Settings

Again, it's very important you know your internet password before you do this.

If you're having an internet issue, that makes things very glitchy. Restart your router. Simply unplug it, wait a minute, then plug it back in and see if the connection returns to normal.

The box your internet provider provides internet access in your home.

I'm glad I was able to help you. Take care, be safe.