What exactly is the point of doing SEO work first of all?
To help increase the online sales or traffic for your own site or client one alike which if you get good enough at this area can pay you like £500 to £50,000 per month depending on your client or what work or tasks you get done for them per job or per month if you learn this skill area right and in a smart way.
Backlinks are still the key right to ranking in search engines is like Google,Bing or Duckduckgo meaning having high quality ones like from say Bestseocompaniesin which is high quality SEO designed to teach you how to rank easier on service through reading the blog or hiring the team behind the website to help you increase your business success.
Onpage has many different factors such as speed is big ranking factor for Google if your site loads slow you need to get it load faster by getting high quality server or good caches or good quality themes or image compressed which can be done by photoshop or by plugins if you use WordPress as well which can be done for you normally fast but picking the right theme is very important one such as Frank is good to fast loading theme but it looks bit boring overall.
Internal linking like this https://www.webverden.com/category/website-designing/ where you link out to other posts or pages you have done before or are doing at the moment to share out the link juice more easily overall.
Have your Google and Yandex and Bing codes on your website to allow the search engines to find your site more easily or help you let them know about the updates easily by doing this through the right codes you need to put onto a website.
Read your Search Console on at least a weekly basis to look for things to improve or make better for you by reading what you get told in your console such as if your traffic dropped or you lost rankings for keywords according to the data you can get told or read by using it to help you each day or week normally.
Check your Google Analytics for information about how to improve your website data and make improvements for a client site by learning from what they tell you such as they say an issue with your site overall.
Have your sitemap sent to search engines so they will get updates sent to their server to allow you to better understand your website or what is going on by your site by sending them a sitemap whenever you do big updates to your online business when you need to do this
Design is important to increase stay site on a site which is also a ranking factor to Google so make sure your site aims to always try and get it going higher and higher when possible such as getting a stay time of 5 minutes would be pretty good overall