Oil mixed in Coolants

Benz A class W169
When coolant indicator blink in dashboard I check the coolant (it mixed with coolant, so I Clean the radiator and replaced new coolant)
Can you guys help me to fix this issue?
I need drawing of coolant system
Do I need to replace Head gasket?
Do I need to replace oil cooler and and it’s gasket ?
Thanks You

few tests:
open bottle cap
step on the gas, hold high rpm short while, let go
check or bubbles come up in your expansion bottle, or even boiling over
if so.. gasket

other (prefered) test: use gas analyser to check for too high levels of HC (Hydro Carbons) in your expansion bottle (sniff the top of the bottle just after opening the cap). HC can only come from leaking head gasket (or maybe egr cooler but that's not possible on an A170)

you might have a oil cooler leaking in the radiator if it is internal to your radiator. check your oil while draining oil pan for coolant. if none "it most likely will" you may just need to replace the radiator. also check level of your trans fluid as this is another posibility.

Does any one can share me a cooling system diagram of this Benz W169
Class A 170
Thank you

Not done one on Mercedes but more generally on other Germany manufacturers and Land-Rover rectangular block style light alloy oil coolers are prone to oil to coolant leaks. Only two tests you can really do if you take the cooler off you could jury rig an air pressure test. T
The other test you could do is for a cylinder head gasket a chemical test for exhaust gas in the cooling water but this will not always reveal a cylinder head gasket.