母国語もずっと使わなければ部分的に忘れていくの英語

In order to master a language, one must give one's days and nights to its study and practice.

involving little use of language

Whatever language you study, you cannot do without a dictionary.

There is no other way of mastering a foreign language than to learn it step by step.

If you would study languages, you should confine yourself to one.

Practice is indispensable to language-study

I learned Japanese before, but now i have forgotten it all even how to say hi...

Learning foreign languages is boring.

You cannot learn too much about your own language.

One who would learn languages, should confine himself to one.

Unless one studies a foreign language, one can not know one's own tongue.

to speak or write a foreign language, in a broken manner

It is not easy [no easy matter] to learn a foreign language.

Practice is the only way to master foreign languages.

The hardest part of language learning is remembering vocabulary.

In order to master a language, you must give your days and nights to its study and practice.

It is by no means easy to master a foreign language.

It is not easy to learn a foreign language.

You must not be afraid of making mistakes when learning a language.

In languages, use is everything.

I'll learn the language before the necessity arises.

I believe a dictionary is necessary when learning a language.

Studying Japanese is difficult at times.

Some children learn languages easily and others with difficulty.

language characterized by excessive use of slang or cant

to pick up a language

The Japanese are weak in languages―poor linguists.

A taste for reading will soon make a linguist of you.

to continue skillfully using a language

I think that it is impossible to master a foreign language by self-learning.