Clutch needs adjustment/replacement Synchonizers worn?
Most likely the clutch-look at disc surface.
Did you use the right transmission fluid or did you forget to maintain your transmission otherwise, your gears are broken and needed to be replaced.. chances are you need a new transmission.
There are many reasons why a car is hard to shift when there is a manual transmission. The clutch is one of the main reasons why a car is not shifting properly. Another reason could be that the transmission is low on fluid.
put petrol in it
As I understand it: Manual: There are a set # of gears (usually 4-6) and you switch between them as required. Automatic: Again a set # of gears (usually 3-5), the transmission switches them automatically, based on current speed and other variables CVT: Instead of having a set # of gears, there is a belt (or chain?) between the only 2 "gears" that exist. Difference being that 1 of those "gears" changes it's circumfrence, giving it an unlimited # of gear ratios. The transmission determines what the appropriate gear ratio should be, based on speed, how hard you press the pedal, load, etc. Hope this helps.
the oil heats up in the transmission and the gears slide easier check the transmission oil and think of a possible change of oil
If you clutch is working fine then try to change the gear fluid in the transmission. My Isuzu shifted hard to and the fluid changed helped alot
you could need a transmission flush or your syncro could be worn. try rev matching between gears and if it shifts smooth by doing that its probably your syncro
Is it an automatic or manual if it's an automatic you may have a bad u joints and same for manual, as well as synchronizing gears may cause it to be hard to shift. Otherwise i'd say it's your u-joints
Automatic: First sign, the fluid is brown (or black) and smells burnt. Also, car shudders on take off or takes a long time to change gears (slips alot). You might even loss reverse and/or first. Manual: Makes noise, hard to shift gears, won't go into gear. Note check oil level in manual tranny. Most people don't
If you are sitting on any kind of slope, your transmission has tension on it, making it hard to change gears. Pull your car onto a level place then try it should be easier. If not then your transmission is messed up.
Each are done differently. and depending on the car. this can be easy or hard. get a Chiltons manual.