freerolls have a lot of variance. in addition to that when the number of players is high it becomes more difficult to win.
The way I do it (the most I have achieved is a 4 and 5 place, playing against 3,500 or more people in both) is the following.
You must first bear in mind that losing is the most natural thing to do, therefore you must abandon the fear of being eliminated. With this I tell you at the beginning of the tournament, play your premium hands strong. once you have taken part of playing strong your premium hands stay in line and play only strong hands .. try to catch a
bluff and keep your stack safe. try to enter award-winning positions, once there it returns to the initial dynamics
Try to win a big hand to raise your rankings and stay there, playing solidly. studying your opponents. And if the variance accompanies you, it is when you will be at the final table, and there you will have another 2 hours of play left hahaha but you will have achieved it and you will be happy!