Hey people, thanks for so many advices. Still up to do more research but that is to your comments it starts to fall in place piece by piece. There's a lot to learn and a bit to purchase but it may actually be a good adventure and who knows what can happen
Later I'll drop a list of lenses I currently have (not going to be amazing list of perfect lenses) so you can tell me (if you'd be so kind of course) if anything could be useful for this one wedding or shall I look for a new lens too... (I forgot to mention that it will be just Civil Partnership ceremony and party, not actual shoot in the church - they're both atheists - so it may be tad easier).