Hello Yeji Song, Your sentences need work. Peachey is right to suggest you post this in Notebook. Think through and think over could be used interchangeably in some situations: after all, if you have something you need to think about it might not matter if you think it through, or over, or both. However, thinking something over means you'll consider it in a general way, whereas thinking something through suggests you'll consider it more carefully, step by step, logically. Peachey and SuKi have given good explanations of thinking something through. So, perhaps you'll think this over, then think through how to correct your sentences.

They are different in meaning. If by 'dictionary' you mean a bilingual dictionary, Mickael, then it's hardly surprising that they appeared to have the same meaning. Bilingual dictionaries are rarely of any use when it comes to deciphering the subtleties of phrasal verbs. 'Think something over' means 'consider'. For example: 'It was an interesting proposition, but I didn't want to decide straight away. So I asked my boss if I could have a few days to think it over'. 'Think something through' means separate something out into its individual parts and stages. This might involve envisaging a plan of action, and deciding what you might do first, and what you would do if things were to go wrong.

I'd actually suggest posting this in Notebook. While some of the phrasal verbs are right, the rest of the sentence has errors. If this helps, "to think (something) through" means to mentally go through the process of something before doing it in practice. If your plan went wrong, that's because you hadn't thought it through.