How to get a higher level?

Read FAQ

https://www.steamgifts.com/about/faq

Ctrl+f What are levels, and how can I increase my level?

give away games. When you make giveaways, the ones that have * on them will give you less xp, the ones with ** will give you no xp. That's the short version, read the FAQ for a more detailed explanation.

indeed most basic thing to do is read FAQ or in this site you could also find discussions related (there are plenty of them :P )

EDIT: I see you have made giveaways, but seems like you don't understand how real CV works read FAQ and note the * and ** when making giveaways