He clearly could have done with more time at Atalanta before making a move to a bigger side but, the striker market being what it is, he got overpromoted relative to his current ability.
Ultimately if he comes good in the coming seasons then we'll say it was a great buy, rightly opting for the long term option in a constricted market. But right now he's out of his depth somewhat, particularly against top level CBs like those Bayern ones.
Last season he averaged 0.44 goals and 0.47 xG per 90 in Serie A. This season he's averaged 0.36 goals and 0.46 xG in the PL/CL combined. I would have been very happy to see him match his last season's rate of returns in his first season in what are tougher leagues, and his xG is pretty much the same at least, but so far he's put away less and has had all his impact in just one competition. Hopefully he hits a run of goals in the second half of the season to pretty up his output.