A few basic tips:
Listen to songs that carry out the style you are looking for, and try to make sense of what its structure is. You can even put it into your DAW to try to tempo-match, and then break it down into how many bars until each section is over. Where's the intro? Where's the outtro? Bridge? How are the dynamics changing over the course of the track?
Common transitions make use of cymbals and other transition sounds, or perhaps drum fills, but good transitions tend to connect both texture and contour (especially when writing orchestral, which has "only" organic instruments). Not just the density of the elements present, but also, the elements should feel like they're working together. Make yourself write a melodic transition sometime, and with time you'll hopefully develop that as simply a core skill. You can do a simple melodic transition by writing a melody that sustains through into the next section, but later on, you could improve it by making all the little elements around the lead work together to lead up to that new section. For an example, I tend to share this, since it's what I consider my personal best arrangement. Maybe it'll help.
Have your friends listen to what you have and give you advice... including us. That means post a WIP, not just "help me".
So sorry to hear about your loss, Nika. I completely understand as I've lost someone recently too...
I hope things get better for you, and I hope you have a reliable network of close friends and family to help you through.
I'm also sorry that I haven't had any updates for a while, I'm still trying to get myself back on track. Pun intended.
Take elements of the things you are transitioning to and from and mix them together.
If you're transitioning from something that is slow and legato to something that is a little faster and more detached, start altering some of the things near the end of the slow section to be more detached, so that the style change doesn't seem to come out of nowhere.
Take themes from the later sections and introduce them as secondary themes in the current section.
Essentially, it's just a matter of introducing stuff in little bits before you get there so that it doesn't seem like you suddenly arrived out of nowhere.