What app ideas to do for mobile app interface design portfolio?

Question

User interface

What applications can you suggest so that you can develop the design of their mobile interfaces in order to put them in your portfolio?
Or maybe where, on what sites, to get these examples or ideas, even if they are initial ones, even if they are just the applications themselves, in order to try to redesign them and put them in a portfolio?
It's legal so that app owners don't complain.
Is it possible to redesign mobile applications, redesign interfaces not in vain for a portfolio, but with the opportunity to earn money? Maybe there are also sites where like contests or something like that is provided?
What applications are now in trend to work out their design?

Answer 1

Design of a mobile application for Pornhub.com Otherwise
, no one is interested in these stores of yours, the weather and other slag.

Answer 2

We go to google play, take some category, and redesign applications in a row if they have jambs. In order to avoid claims, we simply do not indicate that we have redesigned, we change logos and names - it’s enough for a portfolio.