But did Guts like him back romanctically? Im quite bad at interprating romance. Also saw a lot of people online claiming that Guts is bisexual and liked Griffith.
Nothing in the manga supports that idea. Guts' feelings toward Griffith are clearly conveyed throughout the Golden Age as someone he greatly respects and even idealizes a bit, and with whom he develops a close friendship. In parallel, he progressively gets closer to Casca and eventually a true romance blooms between them. You know, generally-speaking, having close friends of the same gender doesn't mean you're gay or bi. And you really shouldn't rely on what random people are saying online to try and understand the story.
the way Griffith acted towards Guts was like he was in love with him.
This statement is actually worth addressing more than the one above. Griffith's feelings towards Guts are ambiguous, and that's on purpose. I think boiling it down to "he must have been in love with him" is overly simplistic, and is doing you a disservice as far as your understanding of the character goes.
From Kentarou Miura's interviews, we know their relationship was modeled on the one he had with his best friend in high school. It was a mix of rivalry and friendship. Of course it's heightened and dramatized in the manga, and the story itself is unrelated, but my point is that the core of it was that: close friendship and rivalry.
In the story, Griffith's reason for wanting Guts in his mercenary band is very practical right from the start: he's an exceptional fighter. Griffith recognizes that and goes to great lengths to ensure Guts fights for him. He comes to rely on him greatly, to the point that in the end, he'd rather kill him than let him leave his grasp. In that sense, Guts was the ace he always had up his sleeve, which also helped him be more at ease psychologically as he tried to accomplish the impossible: rising from a nobody to a king. That's partly why their second duel (and him losing) hit him so hard, as Casca explains to Guts at the waterfall.
The two of them also develop a close bond, and that can be seen as an exception in Griffith's personal philosophy. As he tells Charlotte at the fountain, he doesn't view his mercenaries as his friends, because a true friend has to be his equal. Needless to say, this has a huge impact on Guts, and is what prompts him to leave the band later on. But I think it's shown Griffith did see Guts as a friend regardless of what he said about it, and Guts' emancipation made Griffith see him as a rival as well.
The two aspects above are shown for example when Griffith tasks Guts with "dirty work" that he wouldn't want the rest of his troops to know about, and then (after the queen's death) asks him if his opinion of him is lessened because of it. They can also explain instances where Griffith's behavior is described as "unreasonable" by the characters, like when he personally went to rescue Guts. It's not actually shocking at all that he'd rush to save his friend (and best soldier). Same for Griffith's deranged state of mind after his year of torture. He (wrongly) blames Guts for what happened to him but can't quite come to hate him, instead obsessing over him.
He describes the mix of emotions he feels in volume 10: "hatred, friendship, jealousy, emptiness, frustration, affection, sorrow, pain, hunger..." We see them at play during and after the rescue, where he seems to be confused himself about what he feels at times (he's half-mad at that point). He tries to strangle him, is jealous that he got together with Casca (someone he never cared about romantically), yet he tries to stop his fall when the hand rises during the Eclipse. So it's all a mess, but you'll notice there's no "love" listed in there. And, needless to say, Griffith never shows any romantic disposition towards Guts when they're together (physical or emotional).
So why the ambiguity then? It's really all contained in untold moments. The way he tells him that he'll make him his (which prompts Guts to ask if he's gay, and Griffith to show embarrassment), the jealousy Casca feels towards him, the way he gets to rely on him more and more, takes risks for him, and finally his obsession with him after the year of torture, and what he says when he sacrifices the Band of the Falcon: "only you made me forget my dream". All of this paints a picture where a reader can ask themselves "was it really just an extremely powerful mix of friendship and rivalry or was there more there?"
I think the story and character work perfectly well with that interpretation, that it was the kind of once-in-a-lifetime friendship some people have, mixed with the sort of rivalry that has been known to consume men whole. But I also think Miura, partly through his shoujo manga influences, deliberately made it ambiguous enough that one can wonder if there wasn't yet another kind of feeling added to the mix. One of a romantic nature, although not sexual. However, do note that even if you take it as such, it doesn't negate the rest. Lastly, I believe it's important to remember that while Guts held a special place among his men, Griffith did sacrifice all of the band, which I think says a lot about how he actually felt about everyone in the end.
