How important is it to learn English idioms and slang?

Hi Shannon, I wouldn't learn them at beginner level. There are so many idioms that the chances of you hearing them are very low. Slang is different in different countries, cities and generations. With any vocabulary, if you keep hearing something then look it up. If you live in an English speaking country, you will need to learn them eventually as they are used every day. However, if you use English with non-native English speakers, you are less likely to hear them. Usually people try to learn them around B2 (upper-intermediate level). If you are aiming for Advanced level (professional level) then yes, you will need idioms.

It's very nice to use idioms as it's an advanced level of enhlish and it transforms the speaker to a different level.. I love using ifioms

English is a universal language used globally and stands out among dll other languages.. it's gaining importance and people find it difficult yo survive without the use of this language

If you are living in English country then it is important to learn idioms because they are used in daily conversations.

That depends on for what purpose one is learning English in the first place. Idioms are embedded even in more formal structures of the language. This you will find as you progress through levels of complexity in your journey toward English proficiency. Vernacular, what is referred to here as slang, is a major ingredient of speech when engaging with native speakers and mass media. Interlocution between two non-native speakers will, in all likelihood, be conspicuous by the relative absence of slang. As there are a billion and a half (and growing by the day) speakers of English globally, of which only 400-500 are native, there’s every chance that at any given moment, conversations and social media ‘threads’ will be conducted by two non-native speakers in their lingua franca of English. Idioms and vernacular might not therefore feature so much.

Think of your native language, it has some local expressions or idioms right? So do all languages. So, to be more "native-like" or to understand the target language and the culture better, we need those expressions. And I think no, you do not have to know them as a beginner and yes, they come up very often..