CultofGraphene In WhatsApp I cannot record video at all.
Maybe you need to grant the camera permission to WhatsApp? Long tap on the WhatsApp icon>App info and take a look at it's granted permissions. If camera permission is not granted, do so.
CultofGraphene Duolingo on the other hand when I use the microphone, it can't detect what I'm saying
GrapheneOS is shipped without any speech-to-text app/service (STT), because on stock OS it's a proprietary Google App. You need to install one. There are some OpenSource Apps like Transcribro (availbale e.g. through Accrescent) or Whisper. Some people also use FUTO. There are a lot more. Of course you can also install Google's Speech Recognition & Synthesis - STT-App only - should work with any keyboard like the AOSP keyboard shipped with GOS - or Gboard - Google's Keyboard with built-in STT.
Note: It's the same with TTS (text-to-speech), there's no app/service shipped with GOS. If you need this, e.g. reading some texts or for navigation, you need to install one too. Sayboard or SherpaTTS are two advisable OpenSource Apps.