How to download .docx document to the phone from Google Drive?
You can download docx documents as stated here:

Which file formats can I download?
You can download files in these formats:

Documents: HTML, RTF, DOCX, OpenOffice, PDF, EPUB, Text.
Spreadsheets: CSV, HTML, ODS, PDF, XLSX, TXT (only for a single sheet).
Presentations: PDF, PPTX, TXT.
Drawings: PNG, JPEG, SVG, PDF.


Using version 2.19.013.08.35 of Google Drive, it does not convert docx documents to pdf.

Open Google Drive, go to the folder your file is located.
Click on the 3-dot, then click Download.


If you are still unable to download documents as docx, verify that you have not by mistake converted it to pdf,