Of course, if you are 40 years old now, your memory can't compare with that of young people. So if you have made up your mind to learn English at this time, you must spend more time memorizing words and various grammars. I suggest that after getting up every morning, you must draw for 2~3 hours to recite all kinds of words. According to research, memorizing words in the morning is actually the easiest thing for people to remember.
In fact, if you want to learn English at the age of 40, you must be mentally prepared. If the conditions at home are better, you can hire a private English tutor for yourself, so that you can master all kinds of English grammar more quickly. Of course, now we can also study through the Internet. After all, the Internet is developed now, and there are various learning platforms on it. It's just that 40-year-olds may be slower to accept these new things. We can do it step by step, and there must always be a process. Don't worry.
In addition to hiring a tutor for yourself, you can also consider taking that kind of crash course for adults. Generally, you can attend classes for several hours after work every day. In fact, these crash courses for adults are very effective. Of course, whether you want to learn English at 40 depends on your personal acceptance. If you think your acceptance is good, you can try it.