I cant find the break fluid resevoir in my ar i have an audi a4 1.8 liter manual 4 door 2003

Check up the hydraulic power steering pump.
See picture below for 1.6, 1.8 liters Audi (4 cyl.) engines:

If you find leaks and noise when runing, the hydraulic vane type pump is damaged. The pump **** air inside and mix air with oil resulting foam. Therefore fluid volume inside steering instalation rises. Then pressure overflows oil from the reservoir. You need repair or replace hydraulic vane type steering pump.

1. Pentosin 11S Synthetic Mineral Base Audi Power Steering Fluid

Bilstein 7.1 Mineral Base Audi Power Steering Fluid

sound like your fluid sensor may be stuck or bad if light stays on try tapping the washer motor on the resevoir if it goes out faulty sensor as for the door ajar light it might have bad connection with sensor saying the door is closed local dealer should be able to troubleshoot sensor

you mean brake fluid?
read your owners manual.

As noted in one of the earlier questions on the topic, it appears (will verify for certain after the pump is removed) the plastic resevoir tank has cracked and the hydraulic fluid was lost. Leakage was visible in trunk once spare tire removed.
Audi also noted this is not unusual for a vehicle this age, and the replacement tank is a $100 kit.

If you can't find a dipstick then you probably have to put the fluid back directly into the tranny pan.  There should be a second plug that sits higher up that you take out and then get some sort of pump or tube so you can fill it back up.  I just did this with my Trooper tonight.  Takes a while to get the fluid back in but once it starts dripping back out the fill hole a little you are good to plug it back up.  Thank you for an honest ranking and for using FixYa!

NO, DOT 4 fluid is brake fluid, not power steering fluid. The power steering fluid resevoir is black with a green cap.

HMM, I WANTED SOMETHING FROM YOU BUT HAD TO PAY FOR IT.
YOU WANT SOMETHING FROM ME NOW?
WELL, I WOULD TELL YOU WITHOUT HESITATION OR A REQUIRED PAYMENT.
BUT I JUST ASKED WHAT THE SMALL RECESSED SLOTTED CAP IS FOR, THAT IS TO THE LEFT OF THE MAIN FILLER CAP ON THE BRAKE FLUID RESEVOIR. 2001 S4 AUDI.
IF YOU KNOW PLEASE BE KIND ENOUGH TO ENLIGHTEN ME.BOB

LISTEN CLOSE. THERE IS A PLUG ON PAN. REMOVE IT. WITH A SYRINGE TYPE CANISTER YOU NEED TO INJECT THE FLUID INTO IT UNTIL IT STARTS TO COME OUT. THEN CAREFULLY START VEHICLE AND INJECT ANOTHER 3/4 QUART UNLESS IT STARTS TO COME OUT OR EVEN A QUART.LET IT RUN FOR 5 MINUTES THEN CONTINUE TO INSERT UNTIL IT OVERFLOWS AND TIGHTEN THE PLUG BACK TO THE PAN. i WOULD ONLY USE AUDI VOLKSWAGON FLUID AND YES IT CAN RUN $14 TO $18 A LITER

From my experience, the only requirement is that the fluid is at least DOT 4 rated. There isn't any proprietary brake fluid that I've ever come across.