If the ideology of Marxism as founded by Marx is dialectical materialism then that rules the existence of God out.
Only if you believe that God actively intervenes in the world on a regular and consistent basis, which many Christians don't. The Catholic Church, for instance, has adopted a version of the Deist "God as watchmaker" for the purposes of biological evolutionary theory and many other scientific theories. If the Catholic Church can accept that, then there is nothing preventing Catholics from believing that a historical dialectic exists, with or without God's intervention.
2. I am not hypocrite, but a Communist, as Marx understood it, cannot be a believer in God, just like a Muslim cannot be a believer in the Trinity or the divinity of Jesus. Common sense, right?
Except that Communism, being a secular ideology, does not necessarily dictate that everything Marx said was correct and must be adhered to in the face of overwhelming evidence to the contrary-- while some Communists may indeed take Marx in such a pseudoreligious fashion, many do not, and there is not any inherent ideological mandate in Communism to accept Marx's beliefs as unwavering, infallible and inerrant dogma.
Indeed there have been non-Marxist communist ideologies from the very beginning-- Anarchist Communism, for example, which borrowed some elements from Marx, and was contemporary to early Marxian Communism, but independent of it (and often opposed to it). Even Marx himself acknowledged that communist theory and practice existed before him-- indeed his idea of "primitive communism" was a keystone of his theory, and I'm sure the tribes that practiced "primitive communism" believed in all sorts of superstitions. The Diggers, who were also acknowledged by Marx, were essentially communists, but devout Christians-- and existed over a century before Marx was born.
In short-- your argument=FAIL