That's interesting. I generally used to say couch as well, although I think I also say sofa. But the word sofa comes from Turkish and seems to have invaded most European languages. Although other words exist in each language, sofa (sometimes with some accent like sofá or sofà) works for that item in Spanish, German, French, Italian, Portuguese and Dutch, and probably some languages I don't know. I have found that I now tend to use sofa more often in English as well. But Duo tends to forget to include synonyms when the word is a clear cognate of a common English term. But there is no difference even in style today, although that may have been an original difference. Report it.
You use "acepto" when you're the one who's speaking and you're also the one accepting. You use "acepta" when you're the one who's speaking, but another person (not the one you're talking to, except when that person is an Usted) is accepting. Even if it's your cat accepting and you're talking about it, you use "aceptA".
For the most part you just have to memorize the exceptions. You probably already know some of the exceptions. La mano, el día, el programa. If you know etymology, you might know that programa comes from Greek. Sofá comes from Turkish. Foreign words often disobey the rules. You can still just guess correctly most of the time, but never forget there are quite a few words whose meaning changes only based on the gender like La coma (comma) and el coma (coma)
This story doesn't quite fit, but your thought reminded me of it.
Years ago I visited my (at the time future) husband and at one point he showed me around. During the tour, he pointed out an apartment complex where he and his friends used to live. Apparently while they lived there, the landlord asked them to remove a sofa that some tenant had left jammed in a doorway. Their reward for doing so was possession of the sofa. It took them all day, but they managed it. It was a very comfy sofa, btw.
Fast forward a number of years to my husband and I sitting side by side, watching the latest Ron White DVD. Or rather, he was while I was drawing (soy artista!). Ron White starts talking about making a mad dash out of his apartment, leaving behind his sofa which had gotten wedged in the door...
"That was HIM!?!"
I spent the next half hour trying to erase a rather dark and jagged line that I had not meant to draw.
Spanish is somewhat more staccato than English. But the the pronunciation is absolutely consistent with the written forms. It just takes some time to hear in normal speech flow. I would definitely recommend that you watch videos in Spanish after you watch them in English long before you might consider yourself "ready" . Once you know the plot, you will be able to follow a lot, but you will find that it takes practice and exposure to pick out even all the phrases you know out of a normal conversation flow.
A lounge is not as generally synonymous with sofá as sofa or couch. It is no longer a common piece of furniture, at least in the US, and is designed for reclining on, which a sofa is primarily designed for sitting on. To most Americans if you say lounge they are thinking a room like a teacher's lounge or cocktail lounge, not a piece of furniture at all. When a particular translation can be more misleading than helpful to many users, I think not accepting it is better. Any accepted answer may pop up as a correction. Duo's job is not to prove it has as many alternative translations as you can think up, it is simply to teach you the meaning of the Spanish word. With sofá that is easy. It came into English and several other languages from Turkish. Although the style of sofa has changed from its Turkish ancestor, you can say sofa or sofá in many countries and they will understand.