A stadium (plural stadiums or stadia) is a place or venue for (mostly) outdoor sports, concerts, or other events and consists of a field or stage either partly or completely surrounded by a tiered structure designed to allow spectators to stand or sit and view the event. Most of the stadiums with a capacity of at least 10,000 are used for association football. Other popular stadium sports include gridiron football, baseball, cricket, the various codes of rugby, field lacrosse, bandy, and bullfighting.
Watching football team is allowed provided you avoid sinful acts which can be done by some other fans, and not wasting long time in watching the football. Our time in this life is limited and we must utilize it in useful things for our upliftment and future. Wasting lot of time in watching games makes us lose and miss the aim of our life. Those who waste time will be among the losers and repent a lot when repenting will never help them. Hadeeth from Ahlul Bayt AS) stated that: We were not created for (wasting time on) playing but for big aim.( Tafseer narrated from Al-Hasan Al-Askari).
as salam alaikum
if the environment at the stadium is corruptive or immoral, it is not permissible to attend matches or gatherings, regardless being man or woman. Fans' claims and feelings of superiority, clashes, loosing one's own control, promiscuity, alcoholism, forbidden looks, etc., are often a constant in certain stadiums and promoted by certain factions. That is not appropriate for a Muslim to witness and it should be avoided.
With prayers for your success.