If you find yourself out of space on your web hosting account, you need to upgrade to a higher package. Here is the complete web hosting offer: https://www.host-age.com/web-hosting/.
Can I purchase only additional disk space for my current package?
No, purchasing additional disk space alone is not possible, except for the Enterprise package (which cannot be upgraded) where you can purchase additional space for 2 EUR/month for every 10GB of extra space.