Hi Stefan - Zdravo Stefan,
You worked for free. You don't need to start working without a contract. The client need to hire you first to be able to start.
Please, read the Upwork roles first.
re: "it was fixed price project . and i complete the project . but now client not response me. what can i do ?? kindly help me."
You do not need help. Clients are not required to respond.
You completed the project. You clicked the "Submit Work / Request Payment" button.
Now just wait. Do not click any button again. Do not send messages.
Upwork will release all money in escrow to you AUTOMATICALLY in 14 days.