First - be very VERY careful not to pay and attend a conference that is set up by people just trying to make money. Use search above or Google for 'predatory conferences' to see that there are more VERY BAD conferences being advertised than good and legitimate conferences.
Second - to find a good conference that you are interested in, and would be helpful for you, please check out the websites of societies that cover your areas of interest.
So - to begin you should probably be more specific. Are you only looking for meetings in eastern Europe or all of Europe? Would meetings in the U.S. be possible? There are many meetings, but they are generally not well advertised, as they are usually only on the website of the society.
Many of the sponsored meetings by quality publishers are on more detailed cellular aspects, but some may be good.
There are also some Virtual conferences, such as one on biodiversity in October.
I am hopeful that I might be able to attend an aquatic biodiversity conference in Romania in October. Please just be careful, there are more predatory conferences advertised than quality. Don't be afraid to ask here or message me.
Most conferences and symposiums will not be free as they have to pay for the venue. Many will have a student/early career professional reduced rate if you are just starting your career. Some will also still have a remote-option that is typically reduced-fee, but if you are seeking continuing education credits, they are typically only offered if you are on-site.
Seek out professional societies which are focused on your area of interest, e.g., Waterbird Society, The Wildlife Society (in particular, your local section or chapter), or regional organizations and see when their annual meetings will be.
Otherwise, what area of the world are you in or looking to join conferences at? There are a multitude of conferences hosted worldwide, so knowing where you are able to attend will help others provide useful information.
The Wildlife Society (national) is holding their conference in Maryland in October whereas TWS - western section is holding their conference in northern California in February.
American Ornithological Society is holding their conference in October in Colorado.
Raptor Research Foundation is holding their annual meeting in October in North Carolina
Society of Wetland Scientists annual meeting is being held in November in Taiwan.