I assume you are considered a tax resident of Canada the minute you entered Canada. (unless you can prove otherwise)
For salary earned in HK but received in Canada -not considered taxable in Canada
For dividend earned, you have to report as dividend income.
For stock trading gain/loss
Find out the Fair Market value of these stock on the day you entered Canada and convert them into Canadian dollar. This will be your Adjusted Cost base.
When you sell the stock, the total proceeds minus the Adjusted cost base will be your gain/loss.
e.g.
Original total purchase price + cost = $100,000
Adjusted cost base when you entered Canada = $120,000
Total proceeds = $125,000
Your gain for Canadian tax purposes
$125,000-$120,000 = $5,000.
If considered capital gain, then the taxable capital gain will be 50% of $5,000.
However, if your proceed is $110,000, then you have a loss of $10,000 or taxable capital loss $10,000X50%.
Other issues.
If you have assets outside Canada on the day you entered Canada, you have to obtain the Fair Market of these assets (cash, investments, house etc.)and convert them to Canadian dollar using the exchange rate on that day.
If your assets outside Canada exceeded $100,000, you have to file a T1135 on the second year you file your T1 tax returns.
https://www.canada.ca/en/revenue-agency/services/tax/international-non-residents/information-been-moved/foreign-reporting/questions-answers-about-form-t1135.html
If you have MPF withdraw, you must make some preparation before you receive them.