I loaded the FMC like the plan said. The ZFW is 136 instead of the 122 like the tutorial and I chose 1/3 fuel and full cargo but after I finish everything. The FMC says "No Des Path after NIRSI." Why is this saying that?

Your zfw is off. Something is amiss. (Your figure of 136 sounds like GW ) 1/3 fuel is correct as is full passengers. Did you also adjust your aft and forward cargo holds to 1500 lbs each? Redo your FMC inputs and calculations. You should come out bang on at 122.6 or 122.7. There are also some changes that need to be entered into the FMC if you are using the original nav data that came with the NGX. One of the changes is a speed restriction and that could cause a des path error at the 250 knot hard restriction at sugol.

It was my ZFW but I didn't change the cargo to 1500lbs each. I have up to date NAVDATA from navigraph so I just had to change the 250B/ for REDFA.

FMC thinks that you are unable to descend from 5500 at NIRSI to 2000' at EH621. It's because you're decelerating to flap maneuvering speed. And it's mandatory to fly 220kt at NIRSI. Also they want you to fly low power low drag approach - idle power, gear up, intercept localizer at minimum flap setting (usual flaps 5 will be ok), later flap and gear extension.

If at lower weights you don't have this message, then just be careful on this leg.