Dear Beka,
The only way Collect allows you to export partial data is to use attributes defined in the main entity (or inside single entities of it) and marked with Show in record summary list:
In this way you will see the attribute as a column of the records list and you will be able to sort records in the records list and to filter records by that attribute in the data export page:
Notice that if you have previously collected data and you mark a new attribute with Show in record summary list, you will see a blank column in the record list. If you want to take advantage of it, you will need to export and import the data, overwriting the existing records, and the column will be filled.
Many thanks,
Open Foris Team