hi can you please tell me how can i get umlaut ?
also vielen dank for the corrections

You mean, without German keyboard? Well, on MacOS for instance, you press i.e. the u for long time, and then get a selection of characters: ü, û, ù, ú, ū. Don't know about other platforms (and on Linux, it likely depends on the UI you chose), but if you ask such a question at i.e. stackexchange.com, I think you should get a good suggestion for whatever platform you are using.

Aside from this: In German language, you can in writing replace a ä by ae, ö by oe and ü by ue. It does not look beautiful, but this convention exists, because early typesetting systems (pre-computer era) and mechanical typewriters often did not have umlauts.