"The newspaper is interesting."
well, if you do need help you can go to TTMIK (talk to me in Korean) it will give further information. Since this one is not updated, some things are not accurate. and it might or can be confusing..im still learning Korean with both. i 100% recommend. it lets you even hear how things our supposed to sound in Korean. They have a yt channel which give you the word stem verbs and more things about korean, no im not an advertiser but its still amazing. I hate to see pple struggle soo im giving off a lil secret xd. 계속 한국어를 배우자! (OvO) (Let's continue learning Korean!)
I'm learning too so I might not be of much help, but when you use 은/는, you would be saying "I don't know about other parts of the newspaper (it might not be accurate let's say), but it IS interesting" versus 이/가 would be saying more "I don't know about OTHER newspapers, but this newspaper is interesting." I probably just confused you more but the best thing I'd recommend would be TTMIK (Talk To Me In Korean). They have a really good explanation of the particles. They also explain grammar really well, and it gives you a chance to hear how it's pronounced by a native, and not choppy and computerized.