Hi Shakti Singh
You can absolutely learn a foreign language as an adult, but you need more practice to remember pronunciation, vocabulary or grammar rules. As a kid, you don't study a foreign language as an adult: you just hear new words and repeat them, in class, at home, via games, videos and flashcards.
What I recommend you do to at home is to start watching series or films in your language but with the subtitles on in the foreign language. This will help you to combine the foreign language with your native language. Another good idea is to switch languages on your social media: if you change the settings of your Facebook, Instagram, Twitter and even italki profile to the foreign language, you get in contact with the language every day. Once you've made a bit of progression, you can start to read easy articles and novels in the foreign language.
If I teach a foreign language to an adult-beginner, I start with the pronunciation of the alphabet. As from there, I move on the the basic things: greetings, how to present yourself, numbers, days of the week and months of the year, etc. If I notice these things are going well, I give a first real vocabulary class, about the family or food/drinks for example. I combine these first vocabulary classes with a first grammar lesson about the regular verbs or the article.