I hope you are well today and thank you for your questions.
I tried to import multiple themes from gillion owing to that I have multiple instances of the header menu.
Is there any way to freshly install gillion template?
Do you want to remove all existing conent of your site and install Gillion theme?
If yes then you can remove it using below plugin and reinstall Gillion theme.
Can I reinstall WordPress and again upload zip?
Yes you can.
Will that deactivate my subscription?
No it won’t.