please help me save my partners company

My partner runs a building company and employed me as admin staff back in 2016, together we have grown the company and have reached a stage where we our logo is now recognised by the general public. In December 2017 we won our first new build contact for a residential client, unfortunately in March 2018 I lost my younger brother, the grief took over and my work slipped, with the help of family and the NHS I started to become myself again in November 2018. By the time I was back on my feet and ready to continue work the company had missed payment deadlines, the guys on site had not worked at the speed they should have done, thus leaving us £60,000 short on finishing our new build project. I feel I have let him down and ruined a company he has worked so hard to build, I am now lost as to where I can get the money from.