Dear Zakir Sb, AoA

I am in search of knowing about morning prayers. Rule is we can't offer sunnat prayers after farz. My dad told me today that we can not join jamaat even, if sunnat are not done.

I am trying to offer morning prayers with jamaat and at times I reach, when the jamaat is ready. My intend is to join them as early as possible and I skip sunnat that time. Am I doing wrong? Please help me with Quran and sunaat reference the right path to quote my dad as well as for me.

I am grateful.

Best Regards,
Momin