Alternative to OneDrive

Hi There,
I have been tasked by my company to find an alternative sharing platform for our small business of 5 staff.
We currently use One Drive in order to store and access our files.
What we are looking for is a more reliable alternative to OneDrive free or payable services welcome, which offers the following:
1. All users to be able to access the same drive at one time
2. Certain Files/Folders to be protected (Permission based) so only certain individuals can access them
3. Multiple users to be able to enter, view and edit a document (word/excel) at the same time and the changes saved simultaneously.

I am not from the IT background so any suggestions and help in relation to the above will be greatly appreciated.

Regards
Sarah