My question is if someone is praying a Jum'ah prayer and someone comes to join the prayer and he passes in front of the Maamumah (in front of us) do we have to block him and does he breaks our prayer.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is permissible for whoever wants to join the congregational prayer to pass in front of some praying people and they are not obliged to prevent him. The evidence for this is that Ibn 'Abbaas said: “I came riding a female donkey while the Prophet was leading the people in prayer and he did not have a wall as a Sutrah in front of him, so I passed in front of some praying people and I got down and sent the female donkey to graze and I joined the row, but no one objected to my act.”

Imaam Ibn Hajar said: “Since no one disproved of his behaviour even after concluding the prayer means that this act is confirmed.”

Allaah Knows best.