If you are connection using the TSplus Connection Client,
- Open a client generator, choose "Disable background and animation for better performances".
- In the display tab, choose 15 bits colors.
If you are connecting using the HTML5 web client,
- open an admin tool \ web portal \ HTML5 client
- check the "Use recommended value" box
- refresh your client browser
- right click on "My computer" and click on properties.
- click on advanced system properties, performances, visual effects, and select "Adjust for best performances".
This setting can be set on client and server side and will enhance graphic performance.
Make sure that your graphic adapter drivers are up to date.
Make sure that your RDP protocols and Windows are up to date.