Tenses

[Hanka]

Hello,

could you please check the usage of tenses in the following sentence and possibly other mistakes:

The contractual parties declare that they had and have the opportunity to acquaint themselves with the Rules and that they had done so thoroughly before signing this Contract.

Would it be possible to use past tense instead of the past perfect and why/why not?

Thank you very much

Hanka

[Casiopea]

"had" is simple past. It works. Either delete present tense "have" or add in "still"; i.e., and still have the opportunity to. Past perfect "had done" works. It goes with "before":

The contractual parties declare that they had and still have the opportunity to acquaint themselves with the Rules, and that they had done so thoroughly before signing this Contract.

Event #1: (Past perfect)
had done so; i.e., acquaint(ed) themselves with the Rules

Event #2:
signing this Contract.