I'd also ask Mujtaba's question - I'm not sure what kind of text boxes you are referring to either.
For charts, you can navigate these, either from the sheet or using the elements list - NVDA+f7.
You can also get to notes if that's the kind of text box you're using? Press NVDA+alt+c to read the notes for the current cell. You can also use the Review ribbon to get to the next or previous notes.
If you can advise exactly what you are doing, I'm sure we can help more.
And the Microsoft Excel with NVDA training material which is available from our shop and covers the majority of Excel with NVDA and the keyboard:
https://www.nvaccess.org/shop/
Kind regards
Quentin