Multiple freezes in study mode, almost unusable app

I would like to bring to your attention an important bug: when I am in study mode, every time I put the mind map in full screen I notice a freeze of several seconds before I can start writing on the mind map; then when from the fullscreen on the mind map I decide I want to see my documents, there is another important freeze of several seconds before the documents are visible. What can I do? The app is almost unusable in this way and the file I am talking about is not so large as to justify such an important lag …

PS. I have an Ipad pro 2020 128 Gb (many Gb of space still available) that has never given problems with any other app so far.