I’m not familiar with the g7 but it looks a decent enough option for a first camera. Do mind that it has a relatively small sensor. And if you want to use it for sports something that can do a higher framerate for slow motion might come in more useful than the 4k capabilities.
That said it’s all up to how you use the camera as to how professional it looks. There’s people that make better videos with their Sony a7 for example than others do with RED dragons or such-like.
Once again in certainly no expert on this, if you think it’s the right camera for you, then do it. Of you think it’s not, then don’t.
What you could do is rent one for a day and just try it out to see if it suits you. Just go crazy with it for a day.