Marriage can sometimes be difficult.
true. but then the definition of marriage varies around the world and across cultures
Could you tell me what it means for some other cultures?
for instance, marriage is deemed to be compulsory before engaging in sexual activities
Interesting, but what other differences in the definition of marriages itself are their in other countries?
Not drastic changes. Some for example don't recognize gay marriages. Some recognize child marriages.
And I believe you can still have several legal wives in some countries, right?
Yes, polygamy is recognized within the muslim world.