whats rights should be given to allow user to upload doc using custom webpart

Hi,

Scenario:

I have made custom visual web part to place file uploader (html bootstarp).. where user can upload document which save into

document library....

Requirement:

I just want to allow user to upload document using my custom visual web part …

I have made group which name is "grpUpload' and added all relevant user's here

what rights should be given to this group to not allow user's to see or go into "site contents" and "site settings"...

user's can just see my web part and upload document …. that's all I want

Problem:

1) if I give "contributor " rights so user can go into "site contents" where one can delete/edit/insert items from library which I don't want

2) if I give "restrict read" so user's can not upload document ……..

Guide me please

Thanks