One of the best way of learning is called recycling. That is we read and write sentences that recycle vocabulary several times till we train our mind to recognize it right away. I will type a few words that show the recycling method of learning:
अहम् I
अहं त्वं च I and you.
आवाम् We both.
सः He
सा She
तौ They both
परिवारः Family
मम परिवारः My family.
मम परिवारः अत्र अस्ति My family is here.
अहम् अत्र अस्ति I am here.
त्वम् अत्र अस्ति You are here.
सः च सा अत्र अस्ति He and she are here.
आवाम् अत्र अस्ति We both are here.
त्वम् अत्र अस्ति You are here.
तौ अत्र अस्ति They both are here.
In the above examples you would note recycling of words and at the same time learning sentence structure and new words...that's how it keeps all of standing in this world to learn anything new.
Why do older adults struggle to learn a new language but kids find it much easier?
The reason is because adults have a well developed Declarative Memory ( प्रतिज्ञात्मकः स्मरणशक्तिः )
( pratijnAtmakaH smaraNashaktiH) which has developed over time which includes stored data of life, vocabulary of other languages learnt , in other words the memory that shaped us.
The older the person the more stored data of the Declarative Memory.
Now some of you would be wondering isn't that a good thing?
Well, its good for life as what we call experience but it actually distracts from learning a new language to a certain extent.
There is another type of memory called Procedural Memory प्रक्रमः स्मरणशक्तिः (prakramaH smaraNashaktiH ) which aids learning a new language.
This प्रक्रमः स्मरणशक्तिः (Procedural memory) which develops early in life to learns complex things like grammar rules of a language is more dominant in a child and since a child has not yet developed a fully functioning Declarative Memory ( प्रतिज्ञात्मकः स्मरणशक्तिः ) a child is less distracted to study something new.
In other words as adults we are distracted by the Declarative Memory!
Children are less distracted by the Declarative Memory hence they learn language faster than adults using their Procedural Memory.
Can adults make their Procedural Memory active again as to learn a new language effectively?
Yes!
By focusing on the topic and not try to compare too much with what they think they know. Being repetitive in action is recommended as the Procedural Memory works best for repetitive functions.