Translation:Als er genoeg tijd was, zou ik je helpen.
"Were" is not only the plural form of "was", it's also the past subjunctive in both plural and singular: https://en.wikipedia.org/wiki/English_subjunctive#Use_of_the_past_subjunctive
- If I were you, I would...
- If only he were a bit taller...
Jij is subject, jou is object, jouw is possesive. All these can be replaced by je. In the given sentence you can use either jou or je.
- jij helpt = je helpt = you help
- ik help jou = ik help je = I help you
- jouw hulp is welkom = je hulp is welkom = your help is welcome