The translation suyo reflects the gender and number of the noun it is standing for; theirs is translated by el suyo, la suya, los suyos, las suyas, depending on what is being referred to.
Here is a selection of useful words and phrases you will need in real-life situations while you're visiting Spain and other Spanish-speaking countries...
In Spain the term castellano, rather than español, refers to the Spanish language as opposed to Catalan, Basque etc. The choice of word has political overtones: castellano has separatist connotations and español is considered centralist. In Latin America castellano is the usual term for Spanish.