You can sign it in Chinese if you sign it. When my parents were abroad, they didn't sign in English at first, but they all signed in Chinese, no problem. As for filling in the name, people who don't have an English name can fill in pinyin. In important agreements, you must sign at the end, and it is the official signature you have been using. Never write directly (whether in Chinese or English). In that case, if there is a dispute or forged signature, you can't say it. Moreover, it doesn't matter if you sign Chinese, as long as the signature itself is unique and difficult to imitate. And foreigners praised my mother's Chinese signature for being cool.