1. +랑/이랑, +와/과 and +하고 They mean "and" between nouns. +랑/이랑 and +하고 are spoken. and +와/과 is written. It's up to you. 친구랑 나랑 저녁을 먹었다. - Friend and I ate dinner. 피자하고 샌드위치를 먹었다. - I ate a pizza and a sandwich. 나는 고양이와 강아지를 좋아한다. - I like a kitten and a puppy. 2. +은/는, +이/가 and +을/를 +은/는 and +이/가 are for a subject. Usually, Korean people use +은/는 but if you want to make a point, then you can use +이/가. Actually, in real life, we don't assort thoes. But the usage's difference is like that. Therefore, it's up to you 나는 미국 사람이다. - I am an American. 내가 미국 사람이다. - I am the American. +을/를 is for an object. That's easy to understnad I guess. 나는 콜라를 좋아한다. - I like coke. 3. +하고 있다 and +한다 They are Korean present continous tense. the basic form is +하고 있다. And +한다 is abbriviation of +하고 있다. So they have same meaning. The interesting thing is that +해 is abbriviation of +한다. 나는 숙제를 하고 있다. - I am doing homework. 나는 숙제를 한다. - I'm doing homework. 나는 숙제 해. - I'm doing homework. Plus, if you want to use order form, then you can use +해 with "!". 숙제 해! - Do your homeowork! I hope my explanation will be helpful to you :)

It can be seen as similar meaning, but sometimes it is awkward which one. 1. 나는 사과와 배를 좋아한다(I like apples and pears). 2. 나는 사과, 그리고 배를 좋아한다(I like apples and pears). If there are two words, it is more naturally using '와/과'. And there are more than two words, you would use like this 나는 사과와 배, 그리고 오렌지를 좋아한다(I like apples, pears, and oranges). I hope this answer could help to you :))