And so ... with 于是 — Chinese grammar (HSK 4)

Event，于是 + (Subject) + Following action

于是 (yúshì) means "so / thereupon" and links a past event to the action it led to. It is used in storytelling about what actually happened, not for general cause and effect or for advice. It usually starts the second clause, before the subject.

Examples

下雨了，于是我们决定不出去了。 Xià yǔ le, yúshì wǒmen juédìng bù chūqù le.	It started raining, so we decided not to go out.
他觉得工作压力太大，于是换了一个公司。 Tā juéde gōngzuò yālì tài dà, yúshì huàn le yī ge gōngsī.	He felt the work pressure was too great, so he changed companies.
我找不到那个饭店，于是给朋友打电话。 Wǒ zhǎo bù dào nà ge fàndiàn, yúshì gěi péngyou dǎ diànhuà.	I could not find the restaurant, so I phoned my friend.

Tip: 于是 narrates what happened next; for advice ("so you should ...") use 所以 instead.