"On one hand, you assume that there is certain "beginning" point with NO points before it, on the
other hand you assume that the line is INFINITE, i.e. that there ARE points before any point, so
there ARE points before the "beginning" point."

What I am trying to say is that there must be a beginning point with no points before it, I didn't say there is a beginning point AND the line is infinite. I was saying a beginning point was impossible because there is always points before it, sort of like a never ending chain of cause and effects, but ultimately no cause, just effects.