docx to pdf - upload not possible
no matter what website I get an error: upload not possible:

https://www.google.de/search?q=docx+to+ ... nt=gws-wiz

I use Chrome,
with firefox no problem

You obviously have your reasons, but why do you use an online conversion tool when Libreoffice does the job perfectly?

Or make yourself a service menu.https://imgur.com/a/d5lNOr5 No need to open a s.....d of apps to do this or that when you can bundle the lot of them in servicemenus.
In this case, something like:

[Desktop Entry]
Actions=01PDF;
Icon=application-pdf
MimeType=text/plain;text/csv;text/html;application/vnd.oasis.opendocument.text;application/msword;application/vnd.ms-word;application/vnd.openxmlformats-officedocument.wordprocessingml.document;application/vnd.oasis.opendocument.spreadsheet;application/vnd.ms-excel;application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;application/vnd.oasis.opendocument.presentation;application/vnd.ms-powerpoint;application/vnd.openxmlformats-officedocument.presentationml.presentation;application/vnd.oasis.opendocument.graphics;application/vnd.oasis.opendocument.formula
Name[fr]=Service-Menu PDF convert
Name=convert PDF service menu
ServiceTypes=KonqPopupMenu/Plugin
Type=Service
X-KDE-Submenu[fr]=Convertir en
X-KDE-Submenu=Convert to
X-KDE-Submenu[es]=Convertir a
X-KDE-Submenu[it]=Converti in
X-KDE-Submenu[ru]=&Преобразовать в

[Desktop Action 01PDF]
Exec=soffice --convert-to pdf %F
Icon=application-pdf
Name=PDF
Name[fr]=PDF