How to know my transmission could be to change? (manual)?

hi, i drive a honda civic 2006, i know my clutch is to change since i can hardly accelerate on any type of slope,small like big ones when going up a mountain. I tried going up a mountain and i rev up to red line and still took 10 sec to start going up and the 1st and 2nd gear are becoming hard to go in. But how do i know if one day i have to switch the transmission? Is there a way or im talking about the same thing and im just such a noob anyway thanks for the help

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