Needed third party annotation app major leg

Hi, I bought a Nova Air C because I loved the E-ink color experience and native note-app it brings. Unfortunately, the native app constantly gets stuck when using a specific calendar in pdf. I often use. Therefor being in daily need for another third party annotation app (noteshelf f.i.) in which the calendar does work, I now experience major leg (also after optimizing). There’s not much tips and tricks to find yet for this device, so could someone maybe help me out?