You don’t require attestation of original O levels and A levels certificates. Although British Council provides such attestation service in Pakistan. But it is costly and not required from any German university or embassy. So. dont go for this and save your money.
IBCC and HEC are the Pakistani institutions, so they are not allowed to attest these certificates. Because British Council is the issuing authority of these certificates and only they can attest them.
IBCC equivalence certificate is also not required. Because, it is a local document with no requirement for international universities and embassies.
You just need notary attestation of photocopies of O levels and A levels levels certificates. Then these notaries photocopies send to all the universities for admission. During interview, just show them your original certificates of O levels and A levels.