At my company, people generally work in the same department for about four to five years.
At my company, it is pretty usual for people to stay in the same department for about four to five years.
ご質問ありがとうございます。
① "At my company,"＝「私の会社では」
"people generally work in the same department for about four to five years."＝「一般的に、人々は同じ部署でおよそ4年から5年ほど働きます。」
② "it is pretty usual for people to stay in the same department"＝「同じ部署に人々がいることはかなり一般的です」
ご参考に。
アメリカ合衆国 
