ProjectLibre intends to be an open-source equivalent to Microsoft project. I don't use such software so I can't compare features for you, but I felt it needed to be mentioned.
Your English is quite good, actually.
You could try ProjectLibre from here. Works, but is not nearly as capable as MS Project.
On the other hand, using date math and conditional formatting, it is possible to emulate the calendar aspects of gantt charts using MS Excel. I have a few templates that I used for years that work for small charts up to about 60 tasks or so.
would this be something for you:
https://www.projectlibre.com/products
otherwise you can get a long way on such a small team with just a spreadsheet. And if you want it to be accessible from any device this can be done with google sheets.
You can also look if there are spreadsheet templates that help to make this easier to setup.
ProjectLibre
ProjectLibre is a project management software company with both a free open-source desktop and an upcoming Cloud version. ProjectLibre desktop is a free and open-source project management software system intended ultimately as a standalone replacement for Microsoft Project.
Since construction follows a predictive/waterfall approach you likely want something like MS Project, but free. I am still evaluating freemium and open source options, but I find ProjectLibre to be a decent entry-level replacement https://www.projectlibre.com/
Meanwhile, I would recommend something to keep track off issues and/or tasks (since a Gantt chart isn't a tasklist) - perhaps Trello or one of it's millions of clones? Or perhaps a to do list like Todoist that can do both organized todo lists and Kanban view. Or a phsyical sticky note Kanban.
Obviously you need Excel for some budget estimation and data tracking. Or it's open source and free versions in LibreOffice or Google Sheets (incredible level of formulas nowadays).
If you are in construction, you will need to approve CAD files. You can get any of the free open source CAD programs, but since you will only need to view DWG files and comment on them - get the free viewer DWG TrueView and DWG Review for additional comments https://www.autodesk.com/products/dwg/viewers
Personally I tend to make a lot of graphs and visual guides to get my point across on complicated projects, so I recommend diagrams.net (AKA draw.io)
I think that covers all your bases? You should be good to go.
I have a small Investment Banking firm but not focused on it.... www.marcmergers.com I would be happy to give you gratuitous advice as I am focused on www.projectlibre.com and not taking clients. You can initially look at compatative transactions and be liberal in your search. If anyone suggests a DCF just laugh... there are others that can pivot off the comparative transations etc.... Good Luck
This is a Gaant chart. These are commonly used in project management. The most well known proprietary project manager is Microsoft Project. A great open source alternative is ProjectLibre. There is a community edition that is free to use. It may also be readily available in your distro's repository.
ProjectLibre is an open source replacement for MS-Project. Although not an exact clone of Project, it is similar enough in form and function that you should be able to use it with very little disruption.
It's certainly worth a look if you are comfortable with project and are looking to hit the ground running.