Who is the most serious about baseball in our company?
うちの会社 - our company, this company
野球 - baseball
野球が好き - everyone likes baseball
1番まじめ - most serious
一番まじめは誰ですか? - who is the most serious, who is the most into (intoの意味は興味がある、流行ってるです)
うちの会社で野球が好きで1番真面目な人は誰ですか?
Who is the most serious about baseball in our company?