Among the people that may declare themselves "perfect writers" of the SPANISH language, there is a difference when your proofreading and corrections are put to the test every day.
All the advertising we did there had to be signed by me, therefore, if any written imperfection I was held responsible.
I can proudly say that in 5 years I've never experienced any spelling nor grammar failure in spanish.
Just for you to know, RAE (Real Academia de la lengua Española) has changed some of the rules, I'm just saying this because I know there are native spanish writers that don't know them.
In case you go on another direction, I'll list some of the most common ones so that you can ask for the correction.
It's ok to include some expressions from other languages, examples;
La historia tuvo un happy end de película.
La tensión fue in crescendo hasta que estalló el conflicto.
It's NOT ok to put accents, in any case or use of the word (plural, femenine, etc.), to the following words. You should only see these words if used;
solo (instead of "sólo" this is the most common mistake)
este / esta
ese / esa
aquel / aquella /aquellos
All the best in your assignments,
JaimeCG.