Hi guys!
I'm a Serbian guy, so I thought I'll give you some info regarding Serbia and Crvena Zvezda(Red Star Belgrade).
First of all, unless you're asking for trouble, you should be perfectly safe in Belgrade and Serbia in general. Fans are generally less violent these days as well, and apart from the Belgrade derby games(and even that is more heated in basketball these days than it is in football) there are hardly any incidents, especially unprovoked ones. Food and drinks are very cheap by European standards and most people are very friendly and hospitable. If you for whatever reason can't find a place to stay in Belgrade, the second biggest city Novi Sad(half an hour away buy train, train price around 5 pounds one way) could perhaps be an option, although I wouldn't reccomend it as it would probably require you to use both the train and the taxi later. I would also reccomend asking Liverpool, Spurs and Rangers fans about their experience, if you know any, as I'm sure they'll be able to help you having played Red Star pretty recently. Manchester United played Partizan Belgrade pretty as well. If you have any more specific questions feel free to ask.
As for Red Star, they are Serbia's most successful team both domestically and internationally, famously winning 1990/1991 European Cup(modern day Champions League for those who don't know) as well as Intercontinental Cup the same year. However, since Yugoslavia broke down, all former Yugoslavian teams struggle to really get any notable results in Europe. The state of our league is terrible and all clubs are pretty much state owned (officially not, but they get finances almost exclusively from the government) and the current leading party supports Red Star so they are getting more money than other teams. Before that, we had a same situation with Partizan, hence their dominance 10-15 years ago.
You shouldn't have any trouble beating them if you approach it seriously, but if someone is interested, here's some info about them. Their new coach is an Israeli manager Barak Bakhar, who guided Maccabi Haifa to CL in the previous season where they managed to beat Juventus. He completely changed the way they play. He sets up in a 3-5-2 system and tries to high-press opponents and force them into mistakes. They brought in some really pacy forwards in order to make this style possible. Their danger men(although probably not enough to trouble Manchester City) are Bukari (played for Ghana at the WC and scored against Portugal), Krasso(Ivory Coast international, League 2 team of the season last year), Olayinka(played 5 years at Slavia Prague and was one of their best players) and Ivanic(box to box creative midfielder, caused AC Milan and Rangers a lot of problems in the 2020/2021 and 2021/2022 seasons recpectfully).
You shouldn't be worried about them at all, especially at home. In Belgrade however, you need to take them seriously as many teams who didn't really struggled there. A good example is Liverpool, who lost 2-0 in Belgrade in the season in which they won the CL. TAA was famously subbed off at halftime after looking absolutely lost out there. They also ran AC Milan close in both games in the 2020/2021 season in Europa League round of 32 and were only knocked out because of the away goals rule. The most recent game against European opponent was the friendly against Fiorentina during this seasons' preseason, when they beat them 5-0 in Belgrade(it was 5-0 at halff time as well)
If you take them seriously, I can see you beating them easily like Spurs, Bayern and PSG did, with 5 or 6-0 scorelines. At home you'll beat them comfortably regardless, but if you're not careful they may surprise you in Belgrade.
Hope this helps and if you have any questions feel free to ask.
P.S. I'd also like to point out that they didn't change their name, like I've seen quite a lot of people suggest online, they were always called Crvena Zvezda, it's just that people in England, and in Europe in general, struggle to pronounce it so use the translated name (Red Star, Stella Rossa, Roter Stern, etc).
