I would look for a 2 person tent for a single Person. So you have more comfort and also more space for your backpack and things. the spapeThe shape is not very important for a festival. onlyOnly bring some color tapes with you to mark the strings, otherwise all people will walk over and into your strings and then destroy your tent.
If you want something that is very fast look for some festival a pop up tents. They are open in a sec. because youYou can throw them in the air and they will open by themselfitself.
onOn this webshop you should find some of this tents.