When you migrate your WordPress theme, you should carry few steps before you starts your migration one theme to another.
1. Please create the backup into local/remote server
It is always wise to have the current site’s backup containing your public_html and the database, you can reconfirm your database from the “config.php” from your home directory and do the proper backup by taking all the tables. You might have different size but that is not the case.
2. Content management over the new site from old site
As you have your site is standing to a different URL it can be on the local server or on any remote server where you can easily view your site’s content. Now you also need to figure out what is not right which can be managed over your new site. You can always ask the designer or prepare few good article design who reflects modern and elegant style. You can normally manage your main navigation, Your home page which is the reflection of your website, your sidebar widgets or any other things which are important to have such as your live chat or any third party API authentication.
3. Link Structure and Infrastructure of your new site
When you do migrate you always more focus on the design and the content but above all, there are site links and SEO infrastructure should be focused on your on-page SEO. Always check every link or we recommend to hire professionals like BizzGang. You should copy and make proper data file and then try to evaluate what is not right on your on-page seo.
4. Now as you have your new site ready and we believe you have executed all the above steps and now you can ready to compare your newly build site and you can test all your third party integrations and just keep an eye on the web tools like google analytics and google search console for any bad impacts.