Great. This is perfect, I would just re-arrange this and say, “Retail stores are at risk of disappearing because of the competitive prices of multinational companies that buy almost all their products in bulk.”

Exactly – great example

100 percent right! Just a quick tip. Instead of “more fresh,” you can say, “fresher.”

Here’s the trick: If an adjective is one syllable (hot, cold, fresh, high, low), you form the comparative with -er: hotter, colder, fresher, higher, lower. If an adjective is 3 or more syllables, you always use “more”: more interesting, more difficult, more complicated. If an adjective is 2 syllables, then it’s tricky. If it ends in a -y sound, then use -er (happy > happier, friendly > friendlier); otherwise, use more: “more careful, more peaceful”.

Made works here in English too. A few things for you, then:

• “Their core” – you should specify what you mean by this. I think you mean their primary way of selling or doing business.
• Second, you want to maintain a parallel structure. If you say “from selling” you then need to say “to catering” (note -ing form)

So to keep your original sentence, you can say:

“Skype, WhatsApp, and other apps made Voip companies change their core business from selling in bulk to large carriers to catering to the SMB market.”

It’s a challenge to my brain just writing in English instead of translating Portuguese to English.

Yes, it is. The translation of “made” in Portuguese can have this meaning of “be forced” and that led me the error.

I think you mean: “Before, voip companies sold in bulk to large telecom carriers, but now they are forced to cater to the SMB market because of Skype, WhatsApp, and other apps.” Is that right?