To select multiple files press on as many files as you want to select and check marks will appear next to all of the selected files. OR you press the More options menu icon in the upper right corner of the screen and press Select.

How do I select all in Google Drive on Android?

Alternatively you can click on a file, press Shift on your keyboard and hold it down, then click on another file. This will select all of the files between the first file you clicked and the last file you clicked.

How do I delete multiple files from Google Drive on Android?

To delete multiple files, after left-clicking the first file, hold down the CTRL key and left-click each one of the remaining files you want to delete. Continue to do this until all files have been selected.