Asking for resources for learning design is kind of a broad question.
If you want to focus on designing landing pages, or this is your point of entry, you should just get right into it.
Download a trial of Photoshop, or Sketch, tools are not really that relevant. It just depends on how much time you want to spend expanding your skill set.
Get inspired a lot, browse a lot of websites, and copy whatever you feel like fits.
Some great examples of landing pages for frameworks etc.:
Frameworks are usually a really good place to get inspired in regards to how the pages are designed - what my tool does, how it can help you - remember, most people are drawn to vision, not the exact content of it.
Get inspired with these as well (it's what I use all the time):
Not all of these are web design focused, but sometimes (I find, anyway) even a single image or a color can get me going with a project.
Also, what is extremely important, learn a bit about colors and how users respond to different combinations of them.
A great resource for color paletes that, again, I use all the time:
(last) Also, if you have a colour that you'd like to focus on and expand, check these to help you gather complementary colors:
If you need any help with regards to these tools or otherwise, don't hesitate to message or reach out on Twitter.
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