"Disconnect from xbox live" when I play a certain game.

I would check your download speed on your internet from your xbox, you can find them under settings-network connection and tests. Your ideal download speed should be between 35 and 60mbps. Failing that try contacting your internet provider. for further
assistance contact support here

My Wi-Fi speed is 58 Mbps.

It didn't work... I tried both options but I'm still getting "disconnect from xbox live" when I'm in Gta V.

Thank you so much anyway

I keep getting disconnected from xbox live when I'm playing Gta V.

I have had this a few times when living at a previous address. The problem I had was that the WIFI wasn't strong enough to hold a constant stream for online playing. Most modems have 2 WIFI connection options. 2.5Ghz and 5Ghz. Depending on how far away the
modem is from the Xbox depends on which one you use. If your modem is next to the Xbox use the 5Ghz one and if it's upstairs and far away from your Xbox use the 2.5Ghz. Also remove any boosters connected to your modem as they are not effective and slows down
your WIFI connection.

Other things to try is to restart the modem completely by unplugging the ethernet cable and power cable to release static and to complete a hard reset on the Xbox. Also make sure you have the latest update for the game by checking out your queue list.

Hope this helps!

*RESOLVED *Thanks guys for the help I bought the full game and its letting me online so thanks for the help everyone.