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Hi there. No, there is no other way than backlinks. Basically, the way Search Engines work is that they know what your website (domain) is about and than try to find the best page to match the query. One of the strongest signals engines look at is backlinks. So, if your home page has good backlink profile, secondary page doesn't have any, and Google understands that your website is about, let's say, apples, your index page will be ranking no matter how much you optimize content on secondary page. You can try doing solid internal linking with exact matching anchor text, but I doubt it will help much. Just try to get couple good backlinks to secondary page and you'll be fine.

TL;DR - This can be all or nothing. You must make account in SearchConsole and verify your site. Then you must look pages one-by-one for 90 days period for keywords. If all pages are suddenly drop in one specific date - this can be hit from algo penalty. If they're drop in different times this can be some technical issue. But this also can be due your new site. New sites often get temporary boost in SERP and then they're drop. This is caused from your linking profile and domain/site age. You need little bit patience then to get somewhere in 2x or 1x or even 0x positions in SERP. Just don't rush things with linking. Just little bit patience. That's why - this can be all or nothing. If you're hit from algo penalty then sudden drop everywhere. If you're drop due on different dates can be some technical issue. If you're mixed can be fresh domain, but also check linking profile just to be sure.

Hi, To answer your questions briefly: 1. Redirects should be made on the basis of relevancy. 301's should be made from Home Page to Home Page, Category Page to Category Page, Product Page to Product Page, and so on. You can push your page authority to your Home Page if you really want to, but you will likely see a loss in rankings for the keywords you are targeting. Better to retain that authority for your cabinet keywords and continue ranking with the new site structure while building up the other areas, products and categories. Redirecting to the Home Page will spread your current Authority thin across all aspects of your website, which will limit your rankings across the board. 2. Multiple sub domains will divide the authority of your website. If you can avoid this, do so. It is better to create multiple categories for different products on a single domain, and create relevant link profiles to each category than to create sub domains for each category or product you are providing. If needed, you can create sub domains for each category, but it is a very inefficient and problematic scenario for SEO. Set up your new site to have multiple categories in your Menu, create links to each category page, and only conduct 301 redirects to each category from a relevant category on the old website. Hope this helps - let me know if you have further questions. All the best, Rob