I'm a 5'9 male- is this 51cm frame road bike too small? looking to get into this and after a fair bit of looking I've found this bike. Photos here: https://www.gumtree.com.au/s-view-details.html?adId=1245748386

It says 51cm frame and Medium, but everything I can find online suggests that a medium mens should be 54cm ish? Just wondering if anyone has had experience with the brand or could suggest whether it may be suitable.Thanks!
Most answers to this question will advise you to test the bike, read about fitment, etc. But let’s cut through that - are your body proportions roughly average? If yes, a 51cm is too small for you. 54 is a good target.