Alright,
So still in the terminal, try this.
# Navigate to your home directory
cd ~
# Create a new Downloads folder with proper permissions
sudo mkdir Downloads
sudo chown $USER Downloads
sudo chmod 755 Downloads
# Reset the folder attributes
xattr -d com.apple.FinderInfo Downloads 2>/dev/null
Basically it does, is create a Download folder with the proper permission for the current user, so you.
chown -> change owner, from root to you.
chmod -> change the permissions of read, write and execute.
and xattr is special metadata attached to the Download folder.
At the end, 2>/dev/null is just sending the error if any to /dev/null which is a "void".
One thing that can be done after that is to restart the Finder, to do so:
- Hold the Option key
- Right-click on the Finder icon in the Dock
- Select "Relaunch"