Bangladesh's match with Afghanistan will be more challenging. Sri Lanka was a weak team against Bangladesh. Meanwhile, Afghanistan is a better team than Sri Lanka, so it will be more difficult for Bangladesh to face Afghanistan. Bangladesh is often seen losing easy matches, losing against Sri Lanka is another example. But how they will play against Afghanistan is still doubtful. Yes this is the last chance for Bangladesh but how much they will be able to exploit it is yet to be predicted
Going with the current form, I will not say that Sri Lanka is weaker when compared to Afghanistan. The latter do have some world class spinners. But they are very weak, when it comes to pacers and batsmen. On the other hand, Sri Lanka has a much more balanced side, and most of their players are in great form now. The only negative for Sri Lanka is the absence of their star spinner Wanindu Hasaranga. And now getting back to the Afghanistan vs Bangladesh match, I would say that the Bongs are solid favorites to win, and thereby gain entry to the Super-4 stage.