Started from Nero version 2021, we move all functions of Nero Control Center to Nero Start. So you won't find Nero Control Center any more after installing Nero 2021.
If you want to change the display language in Nero programs, please do below steps by referring the screenshot also.
1. Run Nero Start
2. Click the top-right icon "Support", then sub item "Option".
3. In "General" section, you can set the language as you want.
Please note: New language settings will be applied to Nero Start after next startup.