Yes do this all the time. Look at designs. Bookmark sites. Clip stuff to Pinterest or whatever. Save portfolios of designers you like. Buy design books, they’re always just collections of nice-looking stuff. Copy, look at designs, copy, look at designs, steal, look at designs, copy, look at designs, copy, look at designs, steal, look at designs, copy, look at designs, copy, look at designs, steal, look at designs, copy, look at designs, copy. At first your stuff will look very similar to existing things, the more you do it, the more you’ll merge together in your head all the stuff you’ve looked at & lo and behold original (or ‘original’?) designs will emerge.
All design works like that, it builds upon a million other designs. There isn’t anything that’s really genuinely original, though technology/medium creates spaces for new ways of designing. For visual web/app design, you arrange elements on a screen to make an information display/interface understandable/usable for a user; those elements need not be original.
As an example (from product design), take the iPod: every single bit of that design & every bit of that tech already existed and had been commercially released in various products - from the way it looked (Deiter Rams Braun products from the 60s and 70s), to what it was (Zune etc all preceded it), to the interface (Braun & Deiter Rams again). Ives just took those preexisting things and used his skill (+ a large helping of luck involved in when it was released) to make a complete, excellent design.