Fix several Magento 2.2.1 issues after migrating from 1.9

We are working on the staging site for our Magento 2.2 multistire site. So far we migrated with ubertheme software the data from 1.9. However, we deleted a few sites after migration which is causing issues. We are looking for a team or somebody who is skilled and familiar with Magento 2.2 to solve some issues and after that help with new issues that will arise. We are looking for solutions that are 'clean' so we can update to futire Magento versions without hesitations. We now have the follosing issues Error 1 Open a product and save gives error: - Warning: Illegal string offset 'category_id' in /home2/staging/public_html/vendor/magento/module-catalog-url-rewrite/Model/Category/Plugin/[login to view URL] on line 52 We need to be able to open products and attach them to websites and categories as normal. Error 2 (see attachment) When trying to add a product to a certain category the category is not visible from product page while it is in the categories Error 3 From backend opening – sales – shipments give 404 error when trying to open shipment Our staging website is like [login to view URL] -> [login to view URL] We want to have the multistore functionality online on staging so we can design the different storeviews. After this is done there will be more work until we have a stable Magento 2.2 sites.