I cannot believe I've found it. My mistake was to look for it in english.
The series I was looking for is Time Runners(Yes, it is ITALIAN and it looks like it doesn't have an english wikipedia article).
It was translated to Portuguese via Editora Abril.
I also found a description of the game here but here is the relevant plot:
Episode 1 starts the adventure: we are introduced to the hero, Max,
his girlfriend Jessica and his friend, super-genius Lucas. At the same
time, in a distant future, the Skunks, intelligent robots who enslaved
the humans (mmmhhh... sounds original), lead by their king who calls
himself the Chronodemon, are going to invade various epochs using a
time travel device. Trouble starts when a similar machine made by
Lucas creates an interference, and a Gate opens in Jessica's house -
the stone in the ring that Max gave to her as a present, is of the
same type used by Skunks for time Travel. The robots kidnap Jessica.
Lucas puts a time travel device on a scooter, and Max uses it to start
the risky rescue of his beloved one, ending up in the prehistory,
where he will find some allies...
The italian version had 30 parts. I've found a mention that it was canceled on the 11th chapter, but I cannot confirm. All I can tell is that I can only find up to a Time Runners 8 in portuguese, but this has the "Final battle" title, so I am unsure if they compiled the versions together.
For more info about the game instead of the books, I've found this review of it, and also this gameplay:
I've found this by doing the opposite of usual ID questions. Instead of looking for the story details(that were blurry) I went and looked for who translated things to Portuguese in the 90's. Then I tried looking for the list of published things from them at that time. I went through the catalog from Brasoft first(Which wielded nothing) and then I found this forum post from 2008 with a "List of games Officially released in portuguese", where I saw Time Gate, and then the winner, Time Runners