It depends. It could mean the person speaking was almost fooled by somebody else, or if I threw something at someone for example, they could say "you almost got me" (you almost hit me with whatever you threw)

"Get" is such a common word with several meanings, but if the context is a conversation, it usually means "you almost made me believe you!" (ie. "you almost tricked/fooled me", in Berit's example).

It has many explanations! "You almost caught me", "You almost tricked/fooled me", "You almost gained my interest", "You almost hit/beat/grabbed (any verb that fits the situation)". I would say these are the most common uses :)