Denglish is a bad thing because it alters your mother language. You as a nation and each individual of the nation should do everything is possible to preserve the mother language.
You and 1miau are absolutely right. Using Denglish is not advisable. For most of the languages, Denglish is not entirely necessary. But for some languages, I think we can pardon the use of Denglish.
In conclusion: words which can not be translated can be used as they are; words used worldwide ("manager") can also be used as they are. But words which can be translated must be used in their German form.
Here is why I think that: I'm a Bangla speaker, which is my native language. But there are so many words in English that we don't use their translated meaning. Instead, we speak or write it as it is pronounced. Not that we don't know that meaning or anything. We know the real meaning, but people are used to speaking pronounced English. Like the words
grammar, payment, sports, trading, admin, moderator, report, etc. These are all I can think of at this moment. I'm not saying everyone uses Denglish by default. But for most of us, if you check our local thread, those words are written as pronounced. We have the Bangla meaning. But we don't use that. We are not used to it, and sometimes it may sound funny.
I have an explanation why we use Denglish a lot. First of all, Bengla is a mixed language. Why mix? I'll give the reason. The land where we are located was ruled by different
conquerors at different times. We have a vast history of war, fighting, battles, and rebellion. And every time we were ruled by a party, different cultural heritages were exchanged. That's why we have such a wide variety of words. If you compare from the very beginning, you'll see there are many, many words that didn't originally belong to the Bangla language source but somehow got added to it. People use different bangla in different parts of Bangladesh. Not totally different, but slightly. But if we look at English, it's almost everywhere universal.
My side conclusion: We should avoid using Denglish. But we should use Denglish for most common words. As people are used to that Denglish. If we use translated meaning, some even might wonder what that word is. But the whole point of a translation was for the people to able to understand it.
Everything I wrote above is totally my own personal opinion, from my own perspective. So if you think I did anything wrong, feel free to correct me.