My car is slowed to the front wheels.

Hey friend, brake fluid should be changed every ten to twelve months for safety reasons due to the high temperatures it operates at and its tendency to absorb ambient humidity, even when working in a closed circuit. I recommend you change it because of your problem with the brake lines and the length of time it's been in use.
I hope this helps.

Okay, thanks. Regarding that, I think I've created another problem. On Sunday, the brake on one wheel overheated so much that it was emitting smoke from the caliper, and I think the cylinder seals and the caliper rim might have been damaged. What do you think?

Of course they get damaged by the temperature, but you'll also have to check the wheel bearings to make sure the grease in the bearings and the CV joint hasn't cooked. The brake disc might be warped.

Okay, thanks, that's most likely it, but then will I have to change the bearings too?

Okay, thanks friend, I'll follow your advice, your opinions are very useful to me.