Here are some general advices when encountering issues with your server.
Stay calm. Most issues are less worse than newcomers usually think. For the love of God (or your favourite deity / animal / food), please don't jump into the "reinstallation spiral" thinking reinstalling your server from scratch will magically fix stuff. Reinstalling is a heavy operation and is not a good long-term strategy for fixing problems. You will get tired and won't learn anything.
Search the forum for topics similar to the issue you're encountering. If you have issues with a specific app, you may also want to check the corresponding bugtracker of the app, for example here is the bugtracker for the Wordpress app.
FOR THE LOVE OF GOD, PLEASE provide basic context! Volunteers can NOT help you if you do not take five minutes to describe your context: which kind of hardware, which YunoHost version, what you are trying to do, what you tried, what happened and the corresponding logs.
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