There are several factors to acknowledge before you start a Swedish course. All factors below affect your learning. The first lesson starts of with a survey, to maximize your learning abilities.
Your prior knowledge, i.e. how much Swedish you know already.
Your knowledge of other languages. The more languages you've already mastered, the easier it will be to learn another language.
Your mother tongue. Different languages are more or less "relatied" to the Swedish language, which affects whether learning is perceived as more difficult or easier.
How long you have lived in Sweden.
If your intentions are to stay in Sweden permanently.
Your needs. In what context do you need to use the Swedish language?
Your level of ambition. Is language learning a necessity or "only" a desire?
Your motivation. Is the language course voluntarily selected or appointed by someone else?
Your possibilities to do homework (depends on both your work and family situation). The more hours you spend practising the new language between the lessons, the faster you will learn the new language.
How and to what extent you use the Swedish language today. Do you listen to Swedish radio, do you speak Swedish in your spare time, what are the possibilities for you to speak Swedish at your workplace.
What possibilities you have to expand your daily consumption of Swedish.
What learning style you have, that is, in what way your learn the most optimal way.
Which or what skills you want to focus on (speaking, listening comprehension, writing, or reading). All languages are based on grammar, so some degree of grammar is inevitable.
Possibilitiies to continue the language learning after the end of the course. If you don't keep up using the new language, it'll soon fall into oblivion.
Your linguistic interest and aptitude (which usually go hand in hand).