Where can I find a Buddist Monastery that practice hard training?
Following are some pointers:


https://www.dhamma.org/en/index
http://www.internationalmeditationcentre.org/global/index.html
http://www.buddhanet.info/wbd/
https://www.paaukforestmonastery.org/
https://forestsangha.org/


With regard to the 1st 2 links, there are 10-day courses. In the case of the 1st link, you can progress to longer courses up to 60 days. 3rd link lists many other monasteries and centres which some may allow you to stay up to a year. 4th links gives meditation centres in the Pa Auk tradition which is the best if you are looking to master Jhana. 5th link gives monasteries in the Thai Forrest tradition.