"The faith in both religions is almost identical, the cornerstone of faith in both religions is the absolute oneness of God"
Judaism and Islam are not the only 2 religions believing in the one God that is all good that sends prophets... take Zoroastrianism for instance... would you say that Islam is the international version of Zoroastrianism?
"Christians believe in trinity"
actually, Catholics believe in the Holy Trinity, and they are not considered Christians by all other denominations (Baptists, Pentecostals, Lutherans etc.)
What would you say of Jehovah's witness for instance?
"But Judaism has been a religion only for the jews, the jews didn't think that their religion is a religion for all mankind, till now there are only about 12 million jews world wide"
actually, Jews believe God created all humanity and we are all descendants of Noah. God commanded Noah's sons with only 7 commandments; therefore any human observing these 7 commandments will go to heaven. Jews, however, were set apart from the rest of mankind because God wanted to prove his power through preserving the smallest, most powerless nation of those days, throughout history. all the great empires have fallen but the ancient jews survived. had you told the great Assyrians of the Acadians etc. that the jews will survive to the 20th century while all empires will disappear- it would have been as if you would have told them that water will turn into blood. It's a miracle because it is so inpossible and it is reason God chose the jews: "The LORD did not set His love upon you, nor choose you, because ye were more in number than any people but for ye were the fewest of all peoples"
Deuteronomy 7:7
Jews cannot convert others into their own religion and are not commanded to, so their chances of survival are even smaller. On the other hand it makes Judaism very peaceful- all holy wars in the world were conducted by Catholics or Muslims, trying to convert the whole world into their religion, murdering, imprisoning, torturing others, but Judaism continued to exist through it all without forcing one man to convert to Judaism.
"So my question is,why shouldn't a jewish person believe in Islam?"
Because then they will not be jews any more. They will be Muslims. If that were to happen Jews will be extinct and God will be made a liar who canot prove his existence through preserving his people through history.
"Why should a jewish man believe that Moses, Jeremiah, Isaiah, Hezzekiel are prophets from God but he shouldn't believe in Jesus and Muhamed Pbuh as prophets sent by God"
God gave signs to distinguish between a true prophet and a false one. He said he will send false prophets to test us, and that they will perform miracles etc. but they will persuade us to believe in a different religion and that is how we shoud know they are false: "If there arise in the midst of thee a prophet, or a dreamer of dreams--and he give thee a sign or a wonder,and the sign or the wonder come to pass, whereof he spoke unto thee--saying: 'Let us go after other gods, which thou hast not known, and let us serve them';thou shalt not hearken unto the words of that prophet, or unto that dreamer of dreams; for the LORD your God putteth you to proof, to know whether ye do love the LORD your God with all your heart and with all your soul."
Deduteronomy 13:2-4