some one please explain bmr,tdee and eating back

hi, i needed help with the number crunching.
im 20 yrs old,57 kg and 160cm in height.
i want to loose 7kgs to a GW od 50kgs.
so my bmr is 1290(according to MFP) and 1396.2 by other websites.
MFP has set me a goal to eat 1200 calories.
i excerise 7 days a week minimum one hour a day.
my tdee is 1935 calories (1290* 1.5 =1935 cal even though i work out 7 days a week because i don't do high intensity workout so i think im moderate)
im not sure how to calculate my body fat %beacuse i want to get a accurate bmr (can some one please recommend a good way to calculated this).

for the past month i have been eating 1200 cal and not eating back so netting 600 cal for most days and i wasn't loosing any weight.now i eat half of my excerise cal back so "netting" 1000 calories.but this is below MFP goal and my bmr(im supposed to be netting 1200) i dont see the point in eating all the calories i excerised for.

can some one who is understanding eating back and bmr and tdee help me understand this .

your help is most appreciated.
thanks in advance

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