Car shakes when I try to break.

The rotors are worn / warped and will get worse. Replace them and your pads and your car will love you.

replace the pads or buy new brakes

The Vibration Could Cause The Battery Terminal To Come Loose And If A Battery Terminal Is Loose It Will Make The Car Click But Not Start. Tighten The Battery Terminal And If They Are Dirty Remove And Hit Them With A Wire Brush. Make Sure Not To Get The Residue On Anything As It Will Eat Holes In Anything. It Will Even Remove Paint If Some Gets On The Car. You Can Avoid This By Putting Baking Soda On It To Neutralize The Acid.

For The Shaking It Can Also Be An Alignment Problem, Inflation Problem Due To Not Having The Same Pressure In Each Tire Can Cause On Tire To Not Meet The Road As Well As The Other When Braking. If You Plan On Changing Your Rotors Make Sure They Are Cleaned With Brake Fluid And Use Gloves When Handling Or They Could Squeak Due To The Oils On your Hand Or Any Other Contaminate. Let Us Know If You Need Any Other Help.
Sincerely,
Michael Scott