As with other operating systems, Endless can get slower when many browser tabs and applications are kept open simultaneously.
When in this situation, closing applications or browser tabs will release memory pressure and restore the system to a normal speed.
You can also press the keys alt+f2, write the letter r, then press enter.
This should reinitiate the RAM memory, you should see the desktop flash and respawn back to normal.
If that doesn’t help, try restarting the computer.