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It sounds like a fungal/bacterial infection. If you can provide images, then I can confirm this. Also, it would help me to know your USDA zone, and any other information about the care of the tree, and the climate.

Unfortunately, this just happens sometimes... It happens with many species. They will remove themselves at some point during the year, so it isn't necessary to remove them by hand. It may take a little longer, but they will eventually fall off. There is nothing to be done about this.

This is the Large-leaved Linden, or Tilia platyphyllos. This is quite a large tree. This article will help you with these trees: https://www.gardeningknowhow.com/ornamental/trees/linden/linden-tree-information.htm

The clover-like thing is called Oxalis. It is edible in small quantities, and taste like green grapes. It is also HIGHLY INVASIVE. Make sure that you do not let it go to seed, or any houseplant you have will be so ridden with this stuff that you will never get rid of them. (They have "explosive" seeds pods that launch seeds everywhere.)

This article will give you more information: https://www.gardeningknowhow.com/plant-problems/weeds/managing-oxalis-weeds-in-lawn.htm

This does seem like a fungal infection. The most common cause is soil that remains wet for too long without a period to dry out between watering.

The course of action from here will be a fungicide. This article will help:https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

I would also apply DOLOMITIC LIME and WETTABLE SULFUR to the soil. Continue to do this once or twice per year, especially if you know that it may be a wet year.

This article will help you to grow Linden trees: https://www.gardeningknowhow.com/ornamental/trees/linden/linden-tree-information.htm

This just means that the climate was cooperative, allowing a longer reproduction cycle. Generally this is a good sign of good health of the tree.

This article will give you information on the care of these trees: https://www.gardeningknowhow.com/ornamental/trees/linden/linden-tree-information.htm

I'm sorry about the damage to your linden tree. In this situation, a professional arborist should be consulted. Torn limbs must be pruned or recut in a manner that allows the tree to heal itself before pests and disease take over. You need an honest opinion on whether the tree is worth saving; an experienced arborist will know.