Lookupper does not support real-time translation by design. It is primarily oriented toward language learners, who usually do not need everything translated automatically.
If you need real-time translation, you can try these apps:
LunaTranslator
For visual novels and games with mostly static text. It can hook game text directly without needing to rely on OCR.
WindowTranslator
For other games and apps. However, be aware that WindowTranslator has many performance and usability shortcomings. This is an inherent limitation of real-time translation approaches that rely on OCR, which are extremely resource-intensive.
