Engine off, in Neutral, on a smooth level surface, put it in 1st, may need to rock the bike a bit, now go up thru the gears the same way, if it works okay that way, fire it up & work thru the same way.,just let the clutch out enough to feel the plates start to engage, itll go thru the gears that way, unless something is messed up inside,
I killed mine in 5th once at a lite, I know it will go down thru the gears real quick w/o moving more than a few inches,

How long you been riding? These things generally have great transmissions & may shift a little hard when new, but usually, the internals just dont fail,, bent shift rods arent real common, but they do happen.

Have you gotten rough with it to get it in gear at a lite?

When i had my engine apart i checked the tranny assembly cause i didnt have 5th gear.... someone put an extra friction washer in the case on the clutch side.... and aparently im not the only person to be in the case.... the timing chain was new and the cam tensioner was new.... plus they installed a new oil pump.... with it setting there i can roll it through the gears.... but start it up and it wont go through them at all.... i taped my foot to the sfifter last night and it worked great... but thats not safe at all.... shifter linkage is not hanging up.....