Hello Mary,
If you type fast on your non-German keyboard, it can be time-consuming and annoying to learn how to type on a German keyboard, especially on a virtual one when you cannot see the keys.
If you use the word programme of Microsoft, there’s a section of special signs where you can find the umlauts and then inserts them into your text when you need them.
A bit faster: you can write them at the beginning of each of your German texts and then just copy and paste the respective letter that you need. Or carry all of them all the time in your paste storage: „äöüÄÖÜ“, and every time when you need one of them, paste them and erase the ones that you don’t need.
Or in the word programme of Microsoft you can go to „extras“, then to „autocorrection“ (I assume in your Chinese versions they have different names) and program each „ae“ to turn into a „ä“, etc. But when you write a text in a non-German language, you need to be careful. Because a word like (for instance in English) „aeronautics“ is then turned into „äronautics“ automatically. But that’s no big problem, because you find all these mistakes if you run your text on a spell check. Or if you use the find function for all these ä, ö, etc.
Or if you want to avoid this problem in a non-German language, you can use a combination that you like and that never occurs in the German language. For instance, if you type „aaaa“, it can turn into a „ä“, if you program the autocorrection function accordingly.
All the best,
Tommy