Old school learning
Kiswahili books, dictionaries and courses can be found on different websites. I downloaded, from my point of view, the best of it and gathered it on my Google drive. You can download and print, which makes learning easier.
The only thing to be aware of when learning vocabulary from a dictionary is that there is a lot of vocabulary in dictionaries that typical Swahili speakers in Tanzania won't even be aware of. While I haven't run into this issue personally(because I mostly learned words through interactions rather than from memorizing vocab), I have been warned about this by people before. I recommend supplementing your learning with listening to Swahili through youtube, movies, music, or news. If you don't already have sources on the Google play store you can download ITV's television station app, you can also download an app to listen to Tanzanian Radio Stations, but I haven't tried this to see if it works or is any good.