The storage indicator that you can see on your profile warns you about reaching the free-tier storage limit for long-term files - that limit is 100GB per user. After you reach the limit you can just keep sending more files - but keep in mind that all data stored above that limit will incur a monthly fee according to our storage pricing.
As an alternative you can always clean up old transfers and free up some space:
Read more about cleaning up your files here.
If that doesn't work for you - get in touch with us and we will suit your need for additional space.