I'm studying medicine in 3rd year but I need to have better memory & be more alert, is "arcalion forte" the best for me or u recommend another thing?

Get used to it. My dear, what you're experiencing is the common lot of all medical students everywhere. You could try stimulants but at least here in the States that means either a prescription drug or an illegal drug (except for caffeine). Good nutrition & a good attitude are most important. It will get worse before it gets better, trust me.