Islam as a Religion | Why IT does not make Sense

According to Islam, the Bible has been corrupted and Ishmael is the actual father of Islam. However, by doing some research, we firmly come to the conclusion that Ishmael is only the father of certain Arab nations, not all of them.

Additionally, according to their claims, Isaac is not supposed to be the son of promise, but Ishmael should get this privilege. This belief is by all means irrational because the last Book of the Bible was written 500 years before the birth of Mohammed.