Playing somewhat stronger opponents is fine. If they are too strong it does not make much sense. However, there are a few things you can do that will likely very quickly improve your rating so that you have more opponents of roughly same strength.
1) Make sure you do not hang pieces.
The majority of games at the lowest level is decided by who makes the worst mistakes, blunders a quick mate or just hangs too many pieces. You have to learn to avoid this at all cost! So, play slow time controls and before each move make a blunder check to test whether your move actually hangs a piece (or even just a pawn).
2) Work on your basic tactics.
First, also your opponents will likely hang pieces from time to time. So before really starting to think deeply see whether there is something you can easily snatch off. Further, you should become acquainted with basic tactical patterns such as skewers, forks, discovered attacks, double attacks, and also basic mating patterns. There are plenty of books covering these patterns at a basic level. Note that it is not sufficient to just know the pattern, but you have to solve sufficiently many tactical exercises so that you really know it by heart. At some point you will realize that, at least easy ones, you see instantaneously without actually having to look for them. That is exactly what you want to achieve.
If you do a couple of exercises each day (first sorted by tactical topic, later also mixed problems, where the tactic you're looking for is not given), it is likely that you will very quickly see a dramatic improvement in your games.