Mobile hotspot

Mobile hotspot makes your cellular data connection available to other devices.

The speed of that connection will be entirely dependent on the speed of your cellular data connection.

Contact your cellular carrier if you fell the speed of your connection is insufficent.

Contact your Carrier to increase the speed.

Please see the pic below to make it clearer that Hotspot is enabled by a Carrier on one SIM and not by the other Carrier in the same iPhone (Dual SIM).

Use these steps first

Restart the iPhone or iPad that provides Personal Hotspot and the other device that needs to connect to Personal Hotspot. Make sure that you have the latest version of iOS. On the iPhone or iPad that provides Personal Hotspot, go to Settings > General > Reset, then tap Reset Network Settings.

If Personal Hotspot is not working on your iPhone or iPad (Wi-Fi

Also, check the following

1. Network coverage and stability
2. Data Balance
3. On your windows (See if WiFi Auto Joins is enabled)
4. Also, check if you have any stronger WiFi signal around your computer.

Ask the Carrier to change the SIM if nothing works.