If you have issues with rhythm or tempo here is what I would do. Get out the metronome, put it on a very slow speed, and just clap it. Try accenting the downbeats. If you want t take the clapping to the next level you can try clapping the metronome beat with one hand (or tapping with your foot), and clapping the rhythm with the other. Sometimes even I find getting the coordination for this challenging, so don’t worry if you can’t get it.
Then, with the metronome try just the rhythm on the violin, but without your left hand. While it may be intuitive for your left hand to lead, it should actually be your right hand that’s in charge. Remember to try to add a little accent on the downbeats, this helps to ground the tempo.
Finally add the left hand. Practice only a bar or two at a time. When you feel that you are confident playing it slowly, gradually increase the metronome speed a few ticks at a time. Then try without the metronome.