Certainly creating a robust design that supports multiple screen sizes is no trivial matter. There are tools to make it easier but as with anything else, no single solution fits all developers and all projects. You say you're an experienced web developer and yet you find yourself deficient in this particular skill, so I'm not sure what to think. Maybe your strength lies more in back end programming?
In any case, I suggest looking into frameworks such as Bootstrap or Tailwind. Of course, there are also high-level solutions that don't require as much coding, e.g. WordPress, Wix, Squarespace, etc. WordPress plugins can make it very easy to apply fancy CSS effects without writing any CSS.
As for finding freelancers, I agree that's also a difficult task. I don't have any magic bullet there, other than to prioritize people with good, timely communication skills, and to avoid people on the low end of the price range since they will usually be less experienced.
In any case, I suggest looking into frameworks such as Bootstrap or Tailwind. Of course, there are also high-level solutions that don't require as much coding, e.g. WordPress, Wix, Squarespace, etc. WordPress plugins can make it very easy to apply fancy CSS effects without writing any CSS.
As for finding freelancers, I agree that's also a difficult task. I don't have any magic bullet there, other than to prioritize people with good, timely communication skills, and to avoid people on the low end of the price range since they will usually be less experienced.