Could my Vernee M5 have preinstalled adware? - Android Q&A, Help & Troubleshooting

After two weeks of using my Vernee M5, some adware start showing me banners "inside" applications.
Is it a preinstalled adware? I read it in an Amazon review
I tried Malwarebytes, Avast, Eset... without success.
How could I remove this adware?
Thanks

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As said in the "Vernee M5 Brasil" facebook group, several users reported that 2 applications are adware and possibly spyware.
1. provision (installs several "Poker" apps, and opens webpages)
2. medias (opens several webpages)
Those apps aren't installed on mine, but it's worth mentioning these here.

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I write this post trying to help other people with the mobile telephone Vernee M5.
I do confirm that Vernee M5 has virus/malware in the firmware or at least a security breach that is being exploited.
My wife and I are experiencing the same malware that is being reported here and in the Facebook group of "Vernee M5 Brasil", "android-hilfe.de" and other webs.
Most unwanted applications are aggressive adware, but the security issue is really serious. The pirates have gained access to my Facebook account with the passwords stored in my Chrome Browser. The fraudulent activity in Facebook was reported coming from a chrome browser in Paris, but the pirates can be using a tunnel. Fortunatelly, they have not changed my password and I could gain access to my account and I reported the fraudulent activity. So I guess they can log into other sites with the passwords stored in the phone.
I post some other forums discussing about the malware in the firmware of VERNEE M5
https://www.facebook.com/groups/125454381464394/ "Vernee M5 Brasil"
ACHTUNG! Verdächtige App
@o0Robse0o Habe vorhin endlich nach der Anleitung die SystemApp Aktualisierung mit Funknetz runtergeworfen. Ganz dickes Danke dafür. Prompt blieb das Handy hinterher auch kalt und brauchte viel weniger Strom. Aber zu früh gefreut: kurze Zeit später meldete Avast plötzlich die neue Installation...
www.android-hilfe.de
Sieh dir diese Amazon-Bewertung an von Vernee M5 4G FDD-LTE Smartphone 5.2 Zoll HD, Android 7.0 [4GB RAM+64GB ROM] Octa-Core, 13.0MP + 8.0MP Kamera 3300mAh Akku Fingerabdruckscanner, Band 20 Dual SIM Ohne Vertrag Handy
Achtung!!!
www.amazon.de
The malware is very, very difficult to remove because it is in the firmware and the antivirus cannot even detect the origin of the unwanted automatic installation of applications like QZO, Fake facebook, com.rtycg.erycx, knife thrower, InsTube, etc. Factory reset doesn't clean the malware.
Some users of "Vernee M5 Brasil" have installed a new ROOM through TWRP to get rid of the malware.
I have uninstalled the system app that checks firmware updates of wifi hardware module ( in Spanish was name "Actualización radio firmware" or something similar) with ADB (with USB cable and developer tools enabled) but the problem still persists. Bitdefender, Malwarebytes only detects some fake apps, but they don't fix the real problem. It seems that if the mobile is factory-reset and before connecting to internet and, first of all, the wifi firmware updater app is uninstalled by ADB, it might work. But it didn't worked for me...
Today, the pirates started tagging my contacts of facebook and advertising slimmer products in my name. I guess they gained access by the passwords stored in chrome browser (I didn't have Facebook App installed).
By the way, we bought the phone in Amazon Spain form a seller in Germany. The problems and the apps that keep installing repeatedly every few hours are those reported in "Vernee M5 Brasil". I think Vernee is bankrupt and someone is making cash with the malware.