My MacBook Pro started getting incredibly slow a while back, many tiny processes like opening Mail required a lot of CPU power and took for ever. Until later , a few days ago, it wouldn't startup anymore. It just couldn't get past some error with "disk0s2" or something of that nature.

After a few hours, a timemachine backup and completely new software the Pro would start again. Only all other problems I'd been having before the new software etc. remained the same. So I did a EtreCheck. everything was fine but the HDD, it sayd: "Macintosh HD (disk0s2 - Journaled HFS+) / [startup]: 499.25 GB (177.28 GB free) - 180 errors Drive failure!".

After this I ran all verifications and maintainence procedures of OnyX and actually got a great result. EtreCheck now stated: "Macintosh HD (disk0s2 - Journaled HFS+) / [startup]: 499.25 GB (177.28 GB free) - 27 errors Drive failure!". My MacBook Pro had much less issues than before though I'm not really satisfied.

So I was hoping you could help me out with this issue. I'm buying a new MacBook Pro in 3 months so I'm now willing to invest over €70,- and rather non at all of course. Below is a short discription of my MacBook Pro's hardware just in case.

MacBook Pro 13-inch, Mid 2012
2,5 Ghz Intel Core i5
8 GB 1600 Mhz DDR3
Intel HD Graphics 4000 1024 MB
OS X 10.9.5 (ohh and should I upgrade to OS X Sierra? or keep playing it safe untill I get my new MacBook)

The drive in your Macbook Pro probably has bad sectors. This means parts of the drive can't be read, which could result in data loss.
You can check this with this utility:
https://www.volitans-software.com/apps/smart-utility/

If smart utiity says there's more than 1 bad sector, don't take any risks and replace the hard drive.
A new 500Gb hard drive shouldn't cost you more than around 50 euro.
Although I suggest replacing it with an SSD drive. More costly (150-180 euro for 500GB), but it will speed up your Macbook Pro dramatically. If it's not too old (2010+), it could even save you from buying a new Macbook, depending on what you use it for.

Edit: I see it's a Mid-2012 13" MBP. Definitely worth the SSD upgrade.
One extra thing for the 13" MBP: if Smart Utility says there are CRC errors, then the flat cable connecting the hard drive is damaged, an known problem in these Macbooks. Around 50 euro to replace.

(Bewerkt door Backspin om 14:01, 3-10-2017)