Is it true that Google keeps changing its algorithm? If yes, then how can I get around it and keep the search traffic going up?

https://neilpatel.com/blog/google-algorithm-change/

See, google has a AI (Artificial Intelligence) system and yes it changes, learns the behavior of the user, so i say do some RnD on your competitor, thats the simplest way.

Yes, Sure . To increase traffic on your site I suggest choosing keywords and spying on competitors in choosing keywords and adding them to your site

Yes, it is. You can go around it, all you can do is work more on your content by include the respective keywords to get the traffic you need. Your content should be interactive, I would advice you to include video and photos apart of your content as it will catch the attention of your target audience.