Issues using excell on mac with VoiceOver

Hello everyone. I have to use excell for my studying a lot but i experience lots of issues while using it on my macbook air with VoiceOver. The main issues are that for some reason lots of menu items in the reabon menu are dimmed (not available) in menus when i try to access them. I stop interacting with cells, rows and columns, swipe left until the reabons. I can activate tabs without any issues, but i cannot press on buttons, they are dimmed. What can I do with that? When i try to access these reabons with my keyboard they i collapsed and i can more than one button by pressing tab. The second issue is that when i press the button in this reabon the wineow that should open doesn't open. To open it, i have to press on the needed cell with the mouse, but i cannot do it with voiceover, usually the sited person does that. What can I do with that? This issues are so frustrating! I am using the latest version of microsoft office package, macbook air 2017 macOs 10.14.6.