Icons, logos and marketing stuff are all very different tasks. Many designers will specialise in just those particular disciplines. To take them all on and expect to execute them in a manner which is professional and not distracting, is a big ask.
There are plenty of on-line resources(1) to get started, but be aware that a lot of learning will be required. And that means a lot of failures. If you don't want your failures to be a part of your product/brand etc. then you should hire a professional(2).
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