Should I pray Fajr with the congregation and then pray Isha, or should I pray Isha and then pray Fajr individually, after having slept from Maghrib and woken up for Fajr prayer?

It is better for you to pray 'Isha individually, then Fajr in congregation if you catch it. If you do not catch the congregation, then it is better to pray Fajr in congregation first, then make up 'Isha later, to avoid the disagreement of those who prohibit differences in intention between the Imam and the follower, even though the preponderant opinion is that it is permissible for you to follow him despite the difference in intention. The order of prayers is not obligatory according to the preponderant opinion.