First of all, you'll need to identify where is the leak by yourself.
1) Get a stack of old newspaper
2) Tape them up to form a huge piece of floor plan. Make sure the size equal to engine bay less front wheels
3) Laid the piece of "plan" on your parking lot, secure with heavy stones/bricks at all 4 corners
4) Parked the car on top of the "plan" and leave it over night
5) Wake up with open bonnet, use torch light to shine into your engine bay and look into the "plan" see where the dripping spot is, and directly you can see where the leakage are
* I would be a plus point if you buy mahjong paper in white to be your "plan" for easier identification. But hey, a crap car deserved crap diagnostic

Set those aside, here's a general idea on regular leakage are for D4F engine.
a) Crankshaft bearing oil seal
b) Camshaft bearing oil seal (Same as
a, wait for timing belt change)
c) Oil sump (need to remove entire oil sump for the replacement, suggest wait until next oil change)
d) Oil drain nut seal (ownself use gasket paper cut 1 piece and replace it during next oil change)
e) Flywheel oil seal (wait for clutch replacement)
f) Rocker cover breather valve clogged. Oil get sucked out from the other side of the purge valve and entered into intake hose. Extensive oil sip into combustion chamber, spoil the sparkplug seal(oil doesn't get along with rubber), and leak through sparkplug.
g) Rocker cover breather hose cracked/ruptured, become vacuum leak. Brake pedal become harden, lack of power in cruising speed(no affect when full throttle).
As for your serious power loss, I'd like to try your car by myself before further comment. If you can record a video on your dashboard instrument(both RPM and SPEED need to be on the same screen) while driving, it'll be easier for me to assess what could be the problem.

If not too much hassle, come to SS2/67 KFC look for a very bad conditioned red Shawie, then stand infront of ShabuShabu and shout SATU MELEISIA, HIDUP SAWI x 6 times very loudly, then I'll popped out

Usually it worked in the morning during working days, better chance on Monday and Tuesday. Weekend I no work, so definitely won't be there.
Thanks for your extensive reply.
g) Rocker cover breather hose cracked/ruptured, become vacuum leak. Brake pedal become harden, lack of power in cruising speed(no affect when full throttle).
this is what i feel while driving and when i mentioned pickup is slow. I feel the break padel has become harder and lack of power. ( sorry to hav forgotten to mention that break padel has become harder )
So what do i need to expect if need to repair this . how much dent in the pocket.