How to start learning a second technology/language?

Question

IT education

I want to know how to competently start learning a second technology, have you ever had such a thing in your life that you started learning a second language. I'm a web programmer, I write code in PHP using the Symfony framework, and I really want to start learning mobile development in order to write applications for my phones, I even mastered Kotlin a little. But always when I want to continue to learn a new language, I have thoughts that it is better to devote to mastering the main branch with php, I have already had 3 years of experience in the web and the motivation is not the same. And in mobile development and in the new language of motivation, there is more than enough. For example, I have not yet comprehended a lot of things on the web and therefore I do not know how best to proceed. Please tell me if you have encountered someone like you did, otherwise this throwing from side to side is already tired (