Why do muslims deny that they worship the same God as Christians?

My dear I,m a christian arabic man Jordanian , there a big diffirence between christianity and muslims we say that jesuis is the son of god they say that he is not .jesuis said that no prophets will come after me so mohamed is not a prophet every thing in Islam is forbedden your husbund can marry 4 wives !!!!!!! believe me go to the church and talk to the father to tell you what to do