as salam alaikum
Allah has created the night so that people may better rest and sleep. It is advisable to sleep in the first part of the night and not to go to sleep too late. There are some exceptions in certain days of the year or in relation to certain acts like seeking knowledge and reading the Qur'an. However generally speaking, the believer is not advised to stay awake an amount of time that would weaken his body or psychological state for salat al-layl, salat al-fajr or his daily commitments. Every person needs to adjust their timetable according to their situations and not necessarily sleeping less tantamount to lack of piety.
Having said that, sleeping too much is undesirable. To cut oversleeping habits, it is advisable to pray salat al-fajr as soon as the time enter and not fall asleep after it. If the body gets too tired by not sleeping enough in the morning, it is recommended to sleep a little in the middle of the day.
With prayers for your success