When to Use the Simple Past Tense in English? English Grammar for Beginners

In this video, Alisha answers 5 questions. - What's the difference between 'By myself' and 'on my own'? What's more casual? - What is the difference between suitable and convenient? - When we can use "I was there", "I have been there" and what is the difference? - I have come across a word called "Baller". Could you plz explain what actually it means? - What is correct and why: I have saw or I have seen?