Frankly speaking Bangladesh has never done wonders in test matches and not beaten good teams in test matches. Only some times in their conditions they beaten side like england when they were not at their best but beating any asian team in test matches as they are good against spin as well and main problem is bagladesh dont have good fast bowlers for test matches.
T20 series against Bangladesh will start on 19 Nov 2021 and test will start from 26 Nov 2021. From betting perspective odds will be in favor of Pakistan though I haven't checked yet. I am afraid the way Bangladesh cricket is going, ICC will remove there Test status very soon and that will not be good for Bangladesh future cricket. Bangladesh cricket board must sit and think seriously about there team revival.
I also have not checked but I am 100% sure that pakistan would be clear favorites and odds on pakistan will not be very much. So betting on winning before match can be risky. Yes during inplay odds will change and we may get good odds to place the bet at that time.
Yes they should Improve the quality of their test teams, and may be the series against pakistan could prove good for them.