Olymp Trade’s app is fairly nice, that’s a fact. It has an attractive design and includes all the features you need. Nevertheless, you need to realize that if you’re planning to do some serious trading, the web-platform is way better for that aim than the app. The latter works well as a backup - for instance, when you need to stay away from your PC for a couple of hours. The same is true when you merely trade for the fun of it, without much ambition at all.
However, in case option trading is your business and main source of income, I recommend using both web and mobile platforms. There’s a good reason for that. For example, technical analysis definitely should be done on the web-platform, as the mobile version provides only 5 indicators which may not be enough for that.