Bangladesh won because they perform well both in batting and bowling. Fielding is not that much important as it is in ODI or T20I except the fact you need to be good in taking catches at slip position or near batsmen. NZ know how important second test match will be and they will try to win the match to draw the series. The last test series between both these countries played in NZ also ended in draw 1-1.
Had the pitch in Bangladesh's Sylhet field not been spin-friendly, the result of the first match might have been different as the pace bowling from Bangladesh to New Zealand was very strong and world-class.
Throughout the entire innings of this test match, the spin bowlers dominated, especially Taijul Islam of Bangladesh, he was impeccable.
New Zealand must win the second Test if they want to defend the series.One of the best spin bowlers in the New Zealand team is Mitchell Santner.He was not played in the first test match, maybe the target of the New Zealand team will be to play him in the second test match.New Zealand's spin attack will be a little stronger if Mitchell Santner is included in the squad for their second Test match.