From which parts do all languages consist? We have to develop listening, reading, speaking, and writing skills. But it is impossible without knowing grammar, building your vocabulary, and every language learner has to learn prepositions to verbs, phrasal verbs if to name just a few. Language improvement is a never-ending story even in your language! So which tools may we use?
There are a variety of resources - radio, podcasts, films with subtitles, music(!). Try to find several Youtube channels, where you can listen to videos where all rules are explained in the language from a native speaker. It can be also from a person who has the same mother tongue as you. My recommendations for German learners would be the Easy German Youtube channel and their podcast and Learn German with Anja channel
Of course, it depends on your level, since it is important to find reading information for your knowledge, that might be a bit complicated in the beginning. However, there are adopted magazines for language learners with different levels (easy, middle, and hard). I can recommend you Vitamin.de from Goethe Institut https://www.vitaminde.de/ and magazine Deutsch Perfekt
They also have Instagram pages, so it might be easier for you to bring German to your life through social media. These resources also provide the option to listen and do exercises.
Let me share with you a tip ;) In Germany, there are public bookshelves spread around cities, where you can exchange books, or if you do not have any, just take the one you need. In this way I found a lot of Deutsch Perfekt printed magazines, maybe for some, it would be more convenient to have a printed version. Do not forget about children's books, which you can find on the streets or lend in the library.
Try to find a native speaker, who will become your tandem partner. It is better to speak to someone who is proficient in the language as they can highlight your mistakes. How to find a person? If you have little contact with locals - try to find someone in Facebook groups, write a letter to the local university, visit Couchsurfing meetups, or any kind of gatherings like for Sports or hiking. There is also an application Tandem, where you can find people not only to learn a language with them but also to correct others who learn your mother tongue. All communication goes through private messages.
I find it the most difficult part of learning. The same, find a native speaker or a teacher who can correct you. For English, there is a service Grammarly that might be handy for your English writing skills. Highly recommended!
Some might see it as not very useful because language learning apps we associate with LingueLeo, and Duolingo. Anyway, if you include these applications in your routine, in 6 months' time you will be ready to make a little conversation. Therefore, do not forget about Duolingvo, which can actually develop a good habit in your routine life to spend 15 minutes on the foreign language every day.
Feel free to search for other applications, which can automatically check your grammar, explain rules and build your language proficiency.
We should not forget about regular tutoring or visiting courses. Usually, tutors at language courses will check your writing tasks, speaking, and spelling mistakes. Let's remember, that it is indispensable to learn with a native speaker.
What else? Some coursebooks these days might provide a digital version, so you can do interactive exercises as well as automatically check your correctness.
About online translators... the meaning might be a bit misleading, better choose Oxford or Cambridge vocabulary for English.
Do not forget resources like Spotify or Deezer (really, any platform for music listening), Netflix, Youtube, Instagram... might be great for the process!
At the same time, we all know that to reach good results request regularity, a significant investment of your time and effort, and also money. Do not give up on this long-lasting process. It can be fun, especially when at some moment you ask for a meaningful conversation with a native speaker.