第一句是病句, 语法上虽然没错 help (to) do sth, 但语义上to pitch in并不是help的宾语,而是并列谓语动词, 句子应当是: I'd like to help and pitch in with the dinner. 或省略help, 因为pitch in包含帮助的意思, I'd like to pitch in with the diner.
第二句,simmer不用被动的, 类似中文"鸡汤炖2小时就够了。" 不说”鸡汤被炖2小时...“ The stew simmers for 5 minutes.追问