Mandaly, this is three questions in one. (i found the accents BTW:) Is 'pèdi fil' the opposite of 'pran fil'?, Is it the same as 'pèdi fèy'? How can I use 'pèdi fil'?

pèdi fil is not opposite of pran fil
pran fil - to thrive, to progress

for example, you can say
Biznis li a pran fil.
Her business is growing or thriving.

pèdi fil - to lose esteem, to lose authority, to lose leadership, to lose control, to lose grip
Depi lè zafè eskandal adiltè a, pastè a pèdi fil.
Since the time of the adultery scandal, the pastor's leadership has suffered.

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