Learn Swedish: Teven är mittemot soffan. - The TV is opposite the sofa.

No, mittemot works all by itself. While in English we often say 'across from' or 'opposite to', in Swedish you just put mittemot directly before the noun, as in mittemot soffan (opposite the sofa).

Is the word mittemot made up of smaller words?

Yes, it is a combination of mitt (middle) and emot (against or towards). Put together, it literally translates to 'middle against', which is how Swedish expresses 'opposite' or 'across from'.

Why is 'the TV' spelled teven? Can I write it as an abbreviation?

You can write it either way! Teven is the phonetic spelling where the abbreviation is treated as a regular noun (en teve becomes teven). It is also very common to write TV:n, where the colon connects the capitalized abbreviation to the definite ending.

Why does soffa end in an 'n' in this sentence?

Because it is in the definite form, meaning 'the sofa'. Soffa is an en-word ending in a vowel, so you just add an -n to make it soffan. When describing room layouts, you will almost always use these definite forms to refer to specific furniture.