Hey @MarianV! It seems you are dealing with two different issues:
Sorting and Grouping.
Regarding Sorting: You can only drag rows (records) to re-order them if and only if the table/view you are on is not being "sorted" with specific conditions. If an alphabetical sorting is applied to the base, the only option you have to show the record in a different position is tho change the name of the record/field which is being used for sorting. You can play around with sorting criteria by clicking in "sort", shown on the screenshot below.
If you decide to delete any sorting criteria, only then you can drag records to have them in whatever manual order you decide to.

Regarding Grouping: In order to UNgroup your view/table, please click on this "group" button shown on the image below, and delete any criteria.

Also: I do not want to make things more complex for you, but do remember that you can create multiple views per table. If you'd like to keep your current setup (sorting and grouping) on one place, and have it differently (manually ordered and ungrouped) on a different place, you can create a new view and set specific criteria/configurations for it.

I hope this helps!! Otherwise just let me know.
Mike, Consultant @ Automatic Nation.