Hello, Daniel! It's nice to see that you are trying to make your own sentences. Keep it up! :)

1. tall/taller: Mom is tall father is taller.
Correct: My mom is tall but my father is taller.

2. short/shorter :Chopsticks is short fork is shorter.
Correct: Chopsticks are short but fork is shorter.

3. old/older :Computer is old TV is older.
Correct: The computer is old but the TV is older.