Editing script error

Hello everyone, I am new in Unity, my problem likes the image below, I am surely that my GameObject has rigidbody but when I type it in code, it says… none attached! And I also can’t write void FixedUpdate, is there something wrong with library or anything elsy, please help me, thanks!

.rigidbody shortcut syntax is deprecated. Use GetComponent<Rigidbody>() instead.