Canada visitor record

Hello all! I have a few questions regarding the marriage visa process and visitor record. I recently started a relationship with someone from Canada (came in October to spend a few days and returned in November until now). We plan to get married but he still waiting for a few last papers to start his official divorce process (which hopefully still give entrance in court in the next few weeks) as he is still legally married to his ex-partner, from whom he has been separated for eight years.

Currently, I have an ETA that allows me to stay in Canada for six months, and I am living with him at the moment. My main question is i will need to apply for a visitor record/ an extension as we need more time for his divorce to be done and book our marriage straight away applying after for a spouse visa. He will make a letter saying that is responsible for me and my expenses but I’m worried about the outcome. How does this usually works? How easy is the process online for the visitor record?

I have been living in the UK for seven years and am of Portuguese nationality, while he is a Canadian citizen born. Shall we mention as well that in case the divorce isn’t complete soon we plan to apply for common law partners and for that reason too we need to spend a year living together? Any advice?