"I like to take a walk."
は ≈ "as for..." It takes a concept in general and makes that the topic of conversation. Ex: さんぽはすきです。 = As for walks, they are likeable. = I like walks!
が ≈ "the..." It takes a specific thing and makes that the subject of the sentence. Ex: さんぽがすきです。 = the walk is/will be enjoyable. = I'd like to go out for a walk! / I'm enjoying this trip!
The option to use the keyboard online delete the last word(s) I type when I press enter. That means my answers are always evaluated as incorrect. I'm writing this so the Duolingo Team can fix it, hopefully. (FYI: I use Kitsune on Firefox to type in hiragana while using a regular keyboard)
I wrote something on this before, but since the post seems to have been removed I'll add it again.
散歩 is "a walk", not the act of taking a walk. Taking a walk would be "散歩する", but since you only can combine the copula です with a noun, you'd have to make it one, most likely by adding こと at the end of the verb.
So: "I like to take a walk." = 散歩することが好きです。
Bc: 散歩が好きです。= "I like walks."
It's alot easier to learn by having the kanji. If you are only using duo try kanji tree or kanji senpai. Seriously because without even knowing the reading for some kanji you will be able to get the concept of the sentence because you know the meaning.
Like for today, if you recognize the kanji for now/presently and the one for day then without ever seeing that combination before you know it is today. And since we know the word today, then you know the reading of that combination as well.
Or like knowing school and big then even if you don't know the reading you would be able to guess that big + school is college. Or one + month= 1st month/aka January.
By knowing even a few single, simple kanji you can get the meaning of the sentences better, even if you haven't seen the words before or don't know how to actually say them yet.
Highly recommend studying kanji separately from grammar and vocab study. Focus more on learning the meanings than the readings in the beginning, since the meaning is usually pretty similar even if the readings change. Kanji tree let's you do just meanings if you want and shows the radicals to help you guess the meaning for new ones.