I got some Crash Notifications in the google play console. How could i solve it?

Hi,
my App is on google play and i got some crash notifications from some users. I dont know how to solve it. In the Creator, i have no red and yellow error messages.
Some users are getting these crashes:

(ClassNotFoundException
in BaseDexClassLoader.findClass)

(NullPointerException
in BaseInputConnection.isBracketChar)

(SecurityException
in ff.onTransact)

Hope you can help me. I have already read about logcat, but i dont know how to use it really. I Have tried to open it it but i dont get it to run and i still really dont know where to start.

This is the App: EasyTableNotes - Simple notes in tables

Many thanks and Greetings

Did you search for those error messages both here and in Google?
Try it. It will give you an idea of what is wrong with your app.