Multilingual child

Are there any mommies here who raised their children with 3 languages (or more)? I'm half Cypriot and half Austrian, so I was raised speaking Greek and German, my husband is Slovak and between us we speak English. We live in Austria (which borders to Slovakia), so at the moment I speak only German to the baby, my hubby Slovak and we still communicate in English. For now, I will not be teaching him Greek (he can learn it later if he wants to). Based on what I read this shouldn't be a problem for the child (they can learn up to 6 languages simultaneously), but I'd love to hear from experienced parents. How did you do it? Was the speech delayed? Did the child get confused a lot? Any other advise? Thank you in advance!