I want to hear from experts how can I create videos like the one in the link of this post, like what software to use and where I can find stock photos to compose the stories, any help will be great, please check the link
As Levi says but they'll have been made in something like Illustrator or Photoshop and then imported into After Effects or another animation software.
The illustrations would need to be made or split into lots of layers so the animation can be done and also lots of layers for different mouth shapes and eye states.
There are some rigged character designs out there both free and premium but the problem you'll have is getting stock in the same style and rigged in the way you want it.
When I design characters for animation I always have the animation in mind and design them accordingly.
The whole process is quite involved and not really for the beginner although I believe there are sites that have pre-rigged characters and scenes but I'd imagine they're very limited in what you can achieve with them.