Accurate Translation:
1. 但是 (dan shi)
English pronunciation: dunshr
2. 然而 (ran er)
English pronunciation: raner
3. 不过 (bu guo)
English pronunciation: bugur
If you mean “however many…” it would be 无论多少 (wu lun duo shao)
Example in a sentence:
ENGLISH: "However hard it may be, we must do our best."
MANDARIN: "不管多难, 我们都要尽我们最大的努力去做。"