You were banned for the reason that you're 13 AND from Czech. The discord TOS demands that users from your country be over the age of 15 and holds servers aware of those lying about their age accountable. We're not going to be ones having action taken against us for persons of non-TOS age trying to be in our discord 'server'.
Reading the EU legislature actually, you're not of age to even consent to your information being provided anywhere online - including these forums. As such, I'm locking your account.
fra.europa.eu