Do you agree you cannot be Christian and believe in the theory of evolution?

Of course not.
Here's what Genesis tells Christians: In the beginning, The earth was without form. There was was light before there was matter as we know it. The universe is self-contained and is not the residence of its creator. The Earth is designed to bring forth vegetation. The sea is designed to bring forth animal life. What evolutionist disagrees with any of that?
Now, Genesis also tells us that while "creation" of life itself is inherent in our planet, that God did reserve for himself the hands-on creation of mankind but it does not make-clear exactly what that means. There is no scriptural conflict with the idea that the universe "creates" life-forms - even rather sophisticated ones. As for creating man, the key point of the Genesis story seems to be that God's gift to man of a soul is what separates him from other animals.
Since the details are left to be discerned through exegesis and interpretation there are a number of hypothesis in the Christian community that are each consistent with the Genesis story. My favorite suggests the Eden story illustrates homo sapiens in his animal state: a sophisticated primate without inherent difference from other animals. Again, any good evolutionist will tell you our self-awareness and creative intelligence was not present in early homo sapiens but is an emergent property. I agree and like-minded Christians will tell you the bit about the "forbidden fruit" illustrates this.
"You may surely eat of every tree of the garden, but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die." This is thought by some Rabbinical and Christian authorities to be a metaphor. "Less-than human" animals, including early homo-sapiens, are not intellectually aware of their own mortality nor is one generation particularly discernible from its predecessors. We know lions in Africa today are not the same lions that were there centuries ago, but we also know if you could switch an ancient lion for a modern one no one would notice. Lions lack sufficient individuality for that to matter. "The lions" have always been there as far as history is concerned. So it was with "pre-human" homo sapiens until "we" became more self-aware, more individual, more creative and - significantly - started keeping track.
At that point "we" became something more than a sophisticated primate. We became "mankind" gaining moral judgement and accountability, having unique identities that transcend our common species identity. I would suggest that even in the modern world this is not a universal property, that some are never more than homo sapiens but that's another subject for another day.
So, no, I can't agree with the supposition that a Christian can't believe in the theory of evolution. Genesis seemingly supports evolution as part of God's design and may even be telling us that's where our biological ancestors came from before He picked them to carry our souls.