First Impressions: GMAT practice test - Feedback required

Over the last few weeks, I made the decision to do an MBA in the US. I decided that I'd take the GMAT sometime during July as I'm planning to apply for 2019.

With no preliminary preparation at all, I managed to score a 580 based on the CAT test provided on the 'Manhattan Prep' website. I thought that I had done the test in a very shoddy manner. I didn't know the answering pattern for many of the initial questions for Verbal and Quant. For some odd reason, the graphs and data tables wouldn't load in the Integrated Reasoning section, resulting in nearly ALL questions being answered wrong. I had to select randomly for most questions as the links wouldn't load.

If all of the above didn't happen the way it did, I'm sure I'd have done much better. I have no way of knowing how well I wrote the essay, but I believe that I wrote it with clarity. I could attach/paste it on to this forum if any of you would like to criticize.

Would this be a good indicator for me to set my goals very high? A lot is riding on my GMAT scores as the University that I study in has a very arbitrary grading pattern, and I find it very hard to consistently score high grades (its a humanities course).

Hopefully, if I start preparing now, I should be in a position to score 700+ by July.

This is my first post on this forum. I plan to stick around for a while. Thank you for having me here.