You shouldn't have an infinitive verb follow a subject because it's considered improper conjugation.
1) I'm not sure what you're trying to say here but your verbs aren't conjugated correctly. Furthermore, you're using conocer in the wrong context. Conocer is used to describe familiarity to people and places.
2) Once again, your sentence is grammatically incorrect. The following conjugations for querer in the imperfect tense are yo quería, tú querías, él/ella/usted quería, nosotros(as) queríamos, vosotros(as) queríais, and ellos/ellas/ustedes querían. Your sentence shouldn't have two infinitive verbs next to each other.
3) This sentence is grammatically correct, but you did not follow the directions. The verb saber should be conjugated in the past tense. Your sentence translates to "I want to know Spanish. " I suggest changing this to "Yo supe hablar español."
4) For this one, you could say "Cuando era niño, podía saltar a la cuerda."
5) This sentence does not make sense. It technically translates to "I was going/I used to go to want pizza for dinner." I suggest changing it to "Yo no quería comer pizza para la cena."
