In order to build trust, it's important that we don't hide anything from each other and tell everything that's both good and bad.
ご質問ありがとうございます。
"In order to build trust,"=「信頼を築くために、」
"it's important that we don't hide anything from each other"=「お互いに何も隠さないことが大事である」
"and tell everything that's both good and bad."=「そして良いことと悪いこと、全てを伝えること。」
ご参考までに。