Lexibot is a Telegram bot written on Go, which makes it very easy to add unknown words in the language you learn to your dictionary. You can see how it works below, or you can try it yourself by starting a new conversation with @TheLexibot.
When you start a conversation, Lexibot asks you to configure your language preferences: the language you wish to learn and the interface language.
When the initial setup is complete, you can send a word or a phrase to Lexibot to add it to your dictionary. The bot will try to automatically translate the input and if it is not possible, it will ask you to clarify the translation. You can turn off the auto-translation functionality in the settings.
When you add enough words in your dictionary, you can start the training. Lexibot will ask you to translate a word from your dictionary. You can configure the number of words per trainig in the settings.