I'm watching a "Super Dragon Ball Heroes special" and it has the size of a Dragon Ball Super Heroes anime episode, but it has 2 characters that doesnt appear in the anime, a fight between Gogeta and Vegito (I dont think this fit at all in the anime) and a videogame-like format, after one fight a "K.O.!" sign appears. Is the Super Dragon Ball Heroes special part of the Super Dragon Ball Heroes anime story?
Super Dragon Ball Heroes is an fan-made anime going with great popularity and anything can happen in fan-made animation. Although the release date of Dragon Ball Super 2 is not known yet but if you can read the manga for that if you are excited for that. Current arc if of Goku UI vs Moro is going on in that manga.
"K.O.!" sign appears like a video game because it is promotional anime to promote dragon ball heroes game and cards. According to Wikipedia,
Super Dragon Ball Heroes is a Japanese original net animation and promotional anime series for card and video games of the same name. Similar to Dragon Ball GT, it is a manga-inspired installment of the Dragon Ball media franchise, created by Toei Animation instead of franchise creator Akira Toriyama. It premiered on July 1, 2018. Super Dragon Ball Heroes is presented with several alternate scenarios and possible outcomes within the franchise, taking place after the events of Dragon Ball Super.
In May 2018, V Jump announced a promotional anime for Super Dragon Ball Heroes that will adapt the game's Prison Planet arc. A teaser trailer for the first episode was released on June 21, 2018, and shows the new characters Fu and Cumber, the evil Saiyan. The first episode was shown at Aeon Lake Town, a shopping mall in Koshigaya, Saitama, on July 1, 2018, and was uploaded to the game's official website that same day. Likewise, the second episode was shown at Jump Victory Carnival Tokyo Kaijō on July 16, 2018, before being uploaded to the website.