The certificate is signed by the sololearn founder, and it proves that you have completed a course.. Skills will be upgrading with time, it really has a big value, so of course you can add it to your resume!!!
actually,I think that in a CV is better place some info about your entire account as you are a member of this comunity.A some HR can take a look at your activity and also if your certificates are valid ;)
generally in your CV add the skill not the certificate
only few certificates are important to be added like some Network certificates ex. CCNA certificate or the professional certificates ex. pmp certificate .