This app was mentioned in 8 comments, with an average of 1.63 upvotes
Check out this app called "Deutsch Lernen" on the play store. They create articles on current events aimed at German language learners. They aren't terribly long and the language used is good to grasp but you still end up learning new words. There is also an audio for the article which helps with speaking/pronunciation.
https://play.google.com/store/apps/details?id=pl.luglasoft.deutschlernen
No thats not what i meant sorry. There is an app for android called deutch lernen.
It's videos and articles in german, with embedded translators + a narrator!!
THIS ONE : https://play.google.com/store/apps/details?id=pl.luglasoft.deutschlernen&hl=en
Also Goethe.de offers a free german course coupled with an android app for it.
There's an app called German listening. (android link)
Also try the Deutsche Welle website.
I like this app a lot. It has various podcasts (and their transcriptions) from Deutsche Welle at the levels ~A2-B2. The Top Thema series is really nice, with 2-3 minute audios about various subjects.
Their app is also great. You can listen to news, there is a text underneath it and you can click on words and see them in dictionary.
https://play.google.com/store/apps/details?id=pl.luglasoft.deutschlernen
I gave my B1 exam last month and qualified with excellent marks.
I would like to give you some tips:
Tip 1: Improve your vocabulary. For that I would suggest you the Goethe official B1 wortschatz (vocabulary) : https://www.goethe.de/pro/relaunch/prf/en/Goethe-Zertifikat_B1_Wortliste.pdf
Tip 2 : (Horen) - Give 10 - 15 minutes per day for hearing. Download the following app and listen to 3-4 audios per day.
https://play.google.com/store/apps/details?id=pl.luglasoft.deutschlernen
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Tip 3 : Practice as many model test papers as you can. Do these books thoroughly. These will help you in all four parts. Solutions are available online for these books.
1) https://www.amazon.in/Gehts-Noch-Besser-Testbuch-CDs/dp/8183076319
2) https://www.amazon.in/Zertifikat-B1-Neu-15-Ubungsprufungen/dp/8183076378
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Tip 4 : For sprechen just be confident. Once you have learned the vocabulary, practiced all modeltest papers (including sprechen) and trained your years, you will just glide through.
https://play.google.com/store/apps/details?id=pl.luglasoft.deutschlernen&hl=en
https://www.aqa.org.uk/subjects/languages/gcse/german-8668/subject-content/vocabulary
https://www.ocr.org.uk/Images/68532-vocabulary-list-by-topic.pdf
More advanced vocab (you'll need to make a free account to download):
https://www.tes.com/teaching-resource/as-german-vocab-lists-for-all-topics-6039578
http://www.dartmouth.edu/~deutsch/Grammatik/Grammatik.html
The best overall resource is probably Duolingo:
Viel Glueck! Deutschland ist ein schoenes Land und ich hoffe dir eine schoene Zeit dort.