Shopify SEO - Need Some Help

Hi, my Shopify store is ( www.paulaalure.ca )

I’m looking for some advice and to see how much it would cost someone to do the SEO for my store.

Let’s start with the advice:

Should I be installing an SEO app on my site? is it counter intuitive, or does Shopify handle this better?

Should I be adding a link to every product page saying “pairs beautifully with (product link)” with SEO attached or is this over kill

I’m not entirely understanding how to internal, external, or back link through Shopify?

Should I be SEO ALT text on every image inside my store?

In terms of outsourcing this, I would be wanting to potentially hire someone who knows how to SEO my type of store and to be able to do it on Shopify. What is your rate? Or what is the going rate I should expect for a store like mine?

Any help is very much appreciated, thank you!