does this happen a lot?


Yes. That can happen when you have a weak connection.
It almost never happens at all if you have a strong connection.
How do I fix my disconnect/lag issues?
Check out this video discussing disconnect and lag issues, or read on below!
If you are having frequent issues with disconnects or lag in your games, there are a few things you can try that can improve your connection.
- Clear your cookies and cache regularly! This is the most common fix for any issues of slowness on your computer. See the steps to clear your internet cache here. After you’ve done this, close all browser windows (not just a few tabs, the whole browser!) and re-open chess.com.
- Pause any downloads or uploads on your computer. If you are downloading a large file, this takes up bandwidth and can cause lag.
- Close any other browser tabs that are streaming content. Streaming video or music uses bandwidth just like downloading a large file does. If you’re having connection problems, try pausing your streaming while you play chess.
- Disable browser extensions. Sometimes these use a lot of memory, or alter the JavaScript or other files used by chess.com, or alter your connection in some way. It's best to disable them while playing!
- Check Task Manager to see if any programs are using up a lot of memory, and close them while you play chess.
- If you have a high number of browser tabs open, try closing all tabs except chess.com. Even if you aren’t streaming or downloading, each tab takes up some of your computer’s memory.
- Make sure your browser is updated to the most current version. If you are using Internet Explorer, try using Chrome or Firefox instead. Internet Explorer is no longer updated by Microsoft and many modern websites do not function correctly on Internet Explorer
- Try using a Wired Connection. Sometimes it is an unstable WiFi connection causing the issue. Try being closer to your router, or even using a wired connection.
If you are still having connection issues after all of the above, please contact your internet service provider. You may need a faster connection. Chess.com servers will cancel out up to 1000ms (1 second) of lag, but if your ping is much more than that you may have a hard time playing live chess.
To check your ping, type /ping in the Live chat
https://support.chess.com/article/213-how-do-i-fix-my-disconnect-lag-issues

But I'm playing on the app on my phone...
If other people on your local network are doing things like streaming that can potentially cause issues.
Also, if you have both wifi and cellular data active, that can actually cause problems as the device will try switching between connections and can cause issues.

I was playing a 3 minutes game i had 5 seconds my opponent had 3. All the moves i played from here were pre moves but somehow i lost on time, this has been happening a lot what could be the problem

I was playing a 3 minutes game i had 5 seconds my opponent had 3. All the moves i played from here were pre moves but somehow i lost on time, this has been happening a lot what could be the problem
Premoves take a minimum of 0.1 seconds but can take longer if you're experiencing higher lag or disconnects.
https://support.chess.com/en/articles/8652402-how-can-i-optimize-my-online-chess-performance
https://support.chess.com/en/articles/8584209-how-do-i-fix-my-disconnect-lag-issues